JPH1183886A - Capacitance type microflow sensor, its manufacture, and fixture for externally attaching the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure flow velocities in two directions. SOLUTION: A first and a second detection electrodes 5, 6 are provided on a first substrate 1, and a first measuring recess 10 and a second measuring recess 11 are formed, in the parts of a second substrate 2 around a first boss part 15 and a second boss part 20 respectively; first sensor part communicating passages 16a, 16b communicating the first measuring recess 10 to the outside and second sensor part communicating passages 21a, 21b communicating the second measuring recess 11 to the outside have their respective opening parts oriented in opposite directions. Differential pressure produced by flow velocities works on diaphragms 13a, 13b, so that the capacitance between the first detection electrode 5 and the first boss part 15 and the capacitance between the second detection electrode 6 and the second pass part 20 can become proportional to the differential pressure, the capacitances being derived from flow velocities in opposite directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for detecting the speed of a fluid such as a gas, and more particularly, to a capacitance type micro flow sensor using a semiconductor technology capable of detecting a flow velocity as a change in capacitance. About.

[0002]

2. Description of the Related Art Conventionally, as a so-called fluid sensor, for example, as disclosed in Japanese Patent Application Laid-Open No. HEI 8-114617, a sensing operation section composed of a semiconductor member in a fluid is opposed to a flow of the fluid. It is possible to measure the flow velocity by detecting the change in the resistance value caused by the deflection according to the flow velocity of the sensing operation part, and to use various forms such as those using a hot wire. Some have been proposed (see, for example, Japanese Patent Application Laid-Open No. H7-181067).

[0003]

However, the conventional sensor as described above has the following disadvantages due to its detection principle and the like.
In most cases, the direction of the fluid that can be detected is limited to one direction, and does not enable the flow velocity to be detected in two directions. Further, in particular, there is a configuration in which a flow velocity is detected by a change in resistance value caused by bending of a semiconductor in a fluid as represented by a sensor disclosed in Japanese Patent Application Laid-Open No. 8-114617. However, since the structure is such that the semiconductor portion is directly exposed to the fluid whose flow velocity is to be measured, a large stress is generated in the semiconductor, and there is a high possibility that the semiconductor will be broken. On the contrary, there is a fear that such a measure against the strength may lower the sensitivity of the sensor, and there is a problem that a compromise between the required sensitivity and the strength must be found.

[0004] The present invention has been made in view of the above situation, and can detect a flow velocity in two directions with a relatively simple configuration.
An object of the present invention is to provide a capacitance type micro flow sensor that can be mass-produced by a so-called micro machining technology. Another object of the present invention is to provide a capacitance type micro flow sensor having good detection sensitivity and high reliability. Another object of the present invention is to provide a method of manufacturing a capacitance type micro flow sensor suitable for mass production. It is another object of the present invention to provide a capacitance type micro flow sensor capable of suppressing an output error in a detection circuit. Another object of the present invention is to provide a capacitance type micro flow sensor capable of causing a so-called stagnation point to be generated very near the opening of the communication path of the capacitance type micro flow sensor. Another object of the present invention is to provide a capacitance type micro flow sensor capable of reducing a so-called stray capacitance.
Another object of the present invention is to provide a capacitance type micro flow sensor which is hardly damaged or cracked by an external impact or the like. It is another object of the present invention to provide a method of manufacturing a capacitance type micro flow sensor capable of easily setting a depth of silicon digging. Another object of the present invention is to provide an external fixture that can easily attach a capacitance type micro flow sensor to an injector of a fuel injection device.

[0005]

According to a first aspect of the present invention, there is provided a capacitance type micro flow sensor comprising a first substrate made of an insulating member and a second substrate made of a semiconductor member. The first and second electrodes made of a conductive member are respectively disposed on a surface of the first substrate facing the second substrate, while the first and second electrodes of the second substrate are arranged on the first substrate. A first boss portion facing the first electrode via a predetermined gap and a second boss portion facing the second electrode via a predetermined gap are provided on the surface facing the substrate. Around the first boss, a first recess is provided so that the bottom is a diaphragm, and a second recess is provided around the second boss so that the bottom is a diaphragm. A partition is provided which is recessed and separates the first recess and the second recess. A first communication passage formed between the first concave portion and the second concave portion and communicating the first concave portion with the outside is provided with a first communication passage communicating the second concave portion with the outside. Two communication paths are formed, respectively, and the first communication path is formed by the first electrode and the first main boss part generated according to a pressure difference between the pressure in the first recess and the outside. A change in the capacitance of the capacitor and a change in the capacitance of the second capacitor formed by the second electrode and the second boss portion are configured to be detectable.

[0006] The electrostatic capacity type micro flow sensor having the above-described configuration is provided with two sensors having basically the same configuration integrally, and is capable of measuring two flow velocities. In such a configuration, for example, a glass substrate is suitable as the first substrate, and a silicon substrate is suitable as the second substrate. Then, a space communicating with the outside, that is, a concave portion is formed so as to surround the boss portion between the glass substrate and the silicon substrate, and further, the bottom portion is formed in a thin film shape so as to form a diaphragm. The so-called differential pressure generated by the flow velocity acts on the diaphragm to cause the displacement of the diaphragm, that is, the displacement of the boss. This allows
Since the capacitance between the boss and the electrode changes, the flow velocity can be determined based on the change in the capacitance. In particular, it is preferable that the opening to the outside of the first communication passage and the opening to the outside of the second communication passage are formed so as to face in opposite directions to each other, so that the flow velocity in the opposite direction can be detected.

According to a third aspect of the present invention, in the capacitance type micro flow sensor, a first substrate made of an insulating member and a second substrate made of a semiconductor member are joined to each other. A first electrode made of a conductive member is provided on a surface facing the second substrate, and the first electrode is provided on a side of the second substrate facing the first substrate. A boss portion facing the electrode with a predetermined gap therebetween is provided, and a concave portion is formed around the first boss portion so that a bottom portion becomes a diaphragm, and further, a communication passage communicating the concave portion with the outside. Is formed, and a change in capacitance of a capacitor formed by the electrode and the boss portion, which is generated according to a pressure difference between the pressure in the concave portion and the outside, can be detected. A micro flow sensor, comprising: Is formed to have a predetermined gap with the first substrate facing the flat portion, and a second electrode is provided at a portion of the first substrate facing the flat portion. The second electrode is arranged, the area of the second electrode is set to be the same as that of the first electrode, and a predetermined capacitance generated between the second electrode and the flat portion formed around the concave portion can be output. It is comprised in.

[0008] In this configuration, in particular, a capacitor having the same configuration as that of one sensor portion of the capacitance type micro flow sensor according to claim 1 is further formed with a capacitor having a fixed value. Thus, together with the capacitor for detecting the flow velocity, this capacitor can be used in a detection circuit to which the capacitance type micro flow sensor is connected. Since the capacitor having such a fixed value is made of the same member as the capacitor for detecting the flow velocity, the electrical characteristics of the two are substantially the same, and the ambient temperature and the like when connected and used in the detection circuit. Since the effects are almost the same, it is possible to suppress the influence on the output of the detection circuit and obtain a highly reliable measurement result as compared with the conventional case in which a capacitor made of a different material or the like is used. It becomes.

Further, in the above structure, as in claim 4, the second portion is formed so as to face a plane portion formed around the concave portion so as to form a predetermined gap with the first substrate, and It is also preferable that a third electrode be provided on the first substrate so as to surround the electrode, and the third electrode be held at a predetermined potential outside and used as a guard ring. .

In such a configuration, the second electrode and the second electrode
By providing the third electrode, the lines of electric force between the silicon and the flat portion formed around the concave portion of the substrate are prevented from leaking to the other portions. As a result, generation of so-called stray capacitance is suppressed, and a more reliable capacitance value is obtained.

According to a fifth aspect of the present invention, there is provided a capacitance type micro flow sensor comprising first and second insulating members.
And a central substrate made of a semiconductor member. The first and second substrates are joined to the central substrate so that the central substrate is sandwiched between the first and second substrates. A main detection electrode made of a conductive member is provided on a surface of the first substrate facing the central substrate, and a sub-detection electrode made of a conductive member is provided on a surface of the second substrate facing the central substrate. An electrode is provided, and a main boss portion facing the main detection electrode via a predetermined gap is provided on a surface of the central substrate facing the first substrate, and around the main boss portion, A main measurement concave portion is formed so that a bottom portion becomes a diaphragm, and a communication passage communicating the main measurement concave portion and the outside is formed, while a surface of the central substrate facing the second substrate is formed on the main substrate. The sub boss portion facing the sub detection electrode at a predetermined interval is Scan section and provided on the opposite side, a periphery of the sub-boss portion, and the main measurement concave portion as well as the sub measuring recess on the opposite side of the main measuring recess is recessed,
The second substrate is provided with a static pressure introduction hole having one opening portion in the sub-measurement concave portion and the other opening portion opening to the outside. The change in the capacitance of the first capacitor formed by the main detection electrode and the main boss portion, and the capacitance of the second capacitor formed by the sub detection electrode and the sub boss portion Are each configured to be detectable.

In such a configuration, it is preferable to use, for example, a glass substrate as the first and second substrates, and to use, for example, a silicon substrate as the central substrate, respectively, which have a so-called three-layer structure. Thus, a so-called stagnation point due to the fluid is generated at the entrance of the communication passage, and the measurement accuracy is improved as compared with the related art. That is, when the fluid flows in a direction orthogonal to the thickness direction of the first and second glass substrates and the central substrate, a stagnation point is generated near the center of the three members in the thickness direction. Is located at the opening of the communication passage formed in the central substrate.
The stagnation point in the layer type is shifted from the opening of the communication path to the glass substrate side due to the difference between these two thicknesses, so that more accurate measurement can be performed.

According to a eighth aspect of the present invention, in the method of manufacturing a capacitance type micro flow sensor, the first substrate made of an insulating member and the second substrate made of a semiconductor member are joined. On the surface of the substrate facing the second substrate,
A detection electrode made of a conductive member is provided, and a boss portion facing the detection electrode via a predetermined gap is provided on a surface of the second substrate facing the first substrate. Around the portion, a measurement concave portion is formed so that the bottom portion becomes a diaphragm, and a communication passage communicating the measurement concave portion and the outside is formed, and according to a pressure difference between the pressure in the measurement concave portion and the outside, A method for manufacturing a capacitance-type micro flow sensor configured to detect a change in capacitance of a capacitor formed by the detection electrode and the boss portion, wherein the first substrate is manufactured. A first substrate manufacturing process, a second substrate manufacturing process for manufacturing the second substrate, a first substrate manufactured by the first substrate manufacturing process, and a first substrate manufactured by the second substrate manufacturing process And the second substrate The first substrate manufacturing step includes forming an oxide film on both surfaces of a silicon wafer having a predetermined shape and dimensions, applying a resist on the oxide film, and performing photolithography. By removing the resist in the portion that will be the boss portion and the measurement concave portion by a method, further, after removing the oxide film in the portion where the resist has been removed, all the remaining registers are removed, and the remaining oxide film is removed. Silicon etching is performed on the portion where the oxide film has been removed as a protective film for a predetermined time to remove silicon by a predetermined depth corresponding to a gap between the boss portion and a detection substrate provided on the first substrate. After the first step and after the first step, an oxide film is formed again on both surfaces of the silicon wafer, and a resist is applied on the oxide film;
After removing the resist at the portion to be the measurement concave portion by photolithography, and further removing the oxide film at the portion where the resist has been removed, all the remaining resist is removed, and the remaining oxide film is protected. Forming a measurement concave portion having a desired depth by performing silicon etching on a portion where the oxide film has been removed as a film for a predetermined time. After applying a resist on one surface of the glass substrate, removing the resist at a portion where the detection electrodes are provided by a photolithography method, and then depositing ITO on the entire surface of the one surface,
Thereafter, a step of removing the ITO deposited on the resist by lift-off together with the resist to form the detection electrode is provided.

Such a structure is characterized in that the silicon etching is performed for a preset time so that the depth of the silicon is reduced to a desired size. It is.

According to a ninth aspect of the present invention, there is provided an external fixture for a capacitance type micro flow sensor, the capacitance type macro flow sensor for measuring a flow rate of fuel in an injector used in a fuel injection device. Externally attached to the injector of the electrostatic capacity type micro flow sensor, comprising a main fixture and a sub fixture, the main fixture is a hollow cylindrical shape It has a formed fuel passage, one end of which is fitted with an injector fitting hole into which the end of the injector is fitted, and the other end of which is fitted with one end of a pipe connected to a fuel injection pump. Pipe fitting holes are respectively formed, and a sub-fixture fitting insertion hole into which the sub-fixture is inserted in a direction orthogonal to the fuel passage is formed, and the sub-fixture includes the sub-fixture. Inserted into the insertion hole It has a column fitting portion formed in a columnar shape, and the column fitting portion is a sensor fixing piece in which a part of a semi-cylindrical shape is detachably configured. A semi-cylindrical groove is formed between the portions where the sensor fixing pieces are attached so as to form a part of the fuel passage, and the sensor fixing pieces and the sensor fixing pieces are attached. It is configured such that a capacitance type micro flow sensor is sandwiched between the portion to be attached.

[0016] In such a configuration, an external fixture is provided outside the injector between the injector and the fuel injection pump. Therefore, basically, the fuel passage in the existing fuel injection device is modified. Without applying the method, the capacitance type micro flow sensor can be used for flow velocity measurement.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. The members, arrangements, and the like described below do not limit the present invention, and can be variously modified within the scope of the present invention. First, a capacitance type micro flow sensor capable of detecting a flow velocity in two directions according to an embodiment of the present invention will be described with reference to FIGS. This capacitance-type micro flow sensor has a first substrate 1 made of an insulating member and a second substrate 2 made of a semiconductor member as main components, and the first substrate 1 and the second substrate 2 Are joined, and have basically the same configuration 2
Two sensor units 3 and 4 are configured (see FIGS. 1 and 2). In FIG. 1, for convenience of explanation, three-dimensional coordinates composed of x, y, and z axes are defined as shown in the figure, where the x axis is the first and second substrates 1 and 2. Along the direction of the longitudinal axis of
The z-axis is along the direction of the short axis of the substrates 1 and 2, and the z-axis is along the thickness direction of the first and second substrates 1 and 2.

The first substrate 1 is formed in a rectangular shape using, for example, glass, and has a conductive member, for example, an IT
The first and second detection electrodes 5 and 6 made of O are used as first and second bosses 15 and 2 of the first and second sensor units 3 and 4, respectively.
It is formed at a position facing each of the 0 plane portions. As will be described in detail later, the first capacitor 25 is formed by the first detection electrode 5 and the first boss 15.
Is formed by the second detection electrode 6 and the second boss 20.
Are configured respectively. In addition, the first and second detection electrodes 5, 6 are provided on a plane portion where the first and second detection electrodes 5, 6 are disposed.
In order to enable connection to an external circuit, first and second lead wires 7 and 8 for a sensor portion made of a conductive member such as aluminum are formed, and one end of each of the first and second sensor wires is connected to the first and second sensors. 2 are connected to the detection electrodes 5 and 6,
The other ends are formed so as to be located at the corner portions of the first substrate 1 closest to each other.

On the other hand, the second substrate 2 is made of, for example, a semiconductor member such as silicon and the like.
Are formed. That is, the second substrate 2 has a generally rectangular shape in the xy plane, similar to the first substrate 1. A partition 12 is formed at a substantially central portion of the second substrate 2 in the longitudinal axis direction (x-axis direction) along the short axis direction (y-axis direction).
For example, the first sensor unit 3 on the left side (the left side in FIG. 1) and the second sensor unit 4 on the right side (the right side in FIG. 1) have the same configuration. It is formed to have.

That is, the portion on the left side (left side in FIG. 1) of the partition wall 12 is a portion constituting the first sensor section 3 together with the first substrate 1 and the first detection electrode 5. A first measurement recess 10 having a frame-shaped outer edge in the xy plane is formed. This first measurement recess 10
The bottom of the first measurement concave portion 10 is formed as a thin film having a predetermined thickness when the first measurement concave portion 10 is formed. As a result, a diaphragm 13a is formed.

The periphery of the first measurement concave portion 10 is a frame 14 having the same thickness, and a plane portion facing the first substrate 1 is a bonding surface to be bonded to the first substrate 1. (See FIG. 2). On the other hand, a portion surrounded by the first measurement concave portion 10 is a first boss portion 15, and the first boss portion 15 joins the first substrate 1 and the second substrate 2. In this case, the thickness in the z-axis direction is set so as to just face the first detection electrode 5 with a predetermined gap therebetween (see FIG. 2). Also, the first boss portion 1
5 and the first detection electrode 5 have substantially the same area of the opposing surfaces. The gap between the first boss 15 and the first detection electrode 5 is, for example, about several tens of microns.

Further, the first measurement concave portion 10 and the second substrate 2
The two first sensor portion communication passages 16a and 16b are formed at an appropriate interval in the short axis direction between the first measurement portion and the one end face in the longitudinal axis direction. 10 are communicated through the first sensor section communication passages 16a and 16b. A part of the surface of the second substrate 2 adjacent to the first communication path 16a for the first sensor section is formed at a substantially right angle with the lead-out wiring 7 for the first sensor section provided on the first substrate 1. Is bent so as not to come into contact with the second substrate 2, and a first gap forming notch step 17 is formed (see FIG. 1). Further, a portion adjacent to the first gap forming notch step portion 17 is partially removed so that the xy plane shape is substantially rectangular, and the first substrate 2 is just removed.
First connection portion cutout portion 1 for positioning external connection portion 7a made of a conductive member extending at the end of sensor portion lead-out wiring 7 without contacting second substrate 2
8 (see FIG. 1).

On the other hand, the second sensor section 4 on the right side of the partition wall 12 (right side in FIG. 1) also differs from the second sensor section 4 in that the location where the external connection section 8a of the second sensor section lead wire 8 is located is different. The configuration is basically the same as that of the first sensor unit 3 described above. Therefore, the configuration on the right side of the partition wall 12 will be described focusing on different points,
Regarding the same components as those on the left side of the partition 12 described above, only the names and symbols of the corresponding components will be given.

That is, the second sensor section 4 is located on the right side of the partition 12 of the second substrate 2 as a boundary.
In the second sensor section 4, a second measurement recess 11 is provided as a portion corresponding to the first measurement recess 10 described above. ,
As a portion corresponding to the first boss portion 15, the second boss portion 20 is provided with the first communication passages 16a and 16b for the sensor portion.
The communication path 21a for the second sensor portion
21b are similarly formed on the second substrate 2 respectively. The bottom of the second measurement recess 11 is a diaphragm 13b.

On the other hand, when the arrangement position of the second sensor portion lead-out wiring 8 on the first substrate 1 is set at the center point of the first substrate 1 as the origin, the first sensor portion lead-out wiring 8 is provided. 7, the second gap forming step portion 22 and the second connecting portion cutout portion 23 correspond to the second sensor portion, It is formed at a position corresponding to the lead wiring 8 (see FIG. 1).

Next, the fluid measurement in the above configuration will be described with reference to FIG. First, the static electricity flows such that the openings of the first sensor communication passages 16a and 16b of the first sensor 3 face the steady flow of gas as indicated by solid arrows in FIG. Assume that a capacitive microflow sensor is placed in a gas stream. Under such circumstances, the first sensor unit communication path 16 of the first sensor unit 3
A so-called stagnation point occurs near the openings a and 16b,
The pressure at this point is the so-called total pressure Ptot.

The pressure in the first measuring recess 10 of the first sensor unit 3 also becomes the total pressure Ptot, while the diaphragm of the first sensor unit 3 is provided outside the capacitance type micro flow sensor. 13a vicinity and 2nd sensor part 4
In the vicinity of the diaphragm 13b, a static pressure Pstat is generated. Therefore, inside the first sensor section 3, a differential pressure Pdyn, which is a difference between the total pressure Ptot and the static pressure Pstat, acts on the diaphragm 13a, and the diaphragm 13a
From the inside of the measurement recess 10 to the outside in accordance with the magnitude of the differential pressure Pdyn.

As a result, the distance between the first boss 15 and the first detection electrode 5 increases, and the capacitance C1 of the first capacitor 25 increases according to the increase in the distance, in other words, This shows a change that decreases according to the magnitude of the differential pressure Pdyn. By the way, assuming that the flow rate of the steady flow is Vf, Vf = ｛2 × (Ptot-Psta
It is well known that the relationship t) / ρ｝ ^1/2 holds.

Then, this equation further shows that Vf = α × (Pt
ot-Pstat) ^1/2 . Where α =
(2 / ρ) ^1/2 . Ρ is the density of the fluid. In this equation, (Ptot-Pstat) is the differential pressure Pd
yn, and the differential pressure Pdyn can be detected as the capacitance C1 as described above. Therefore, if the relationship between the capacitance C1 and the differential pressure Pdyn is checked in advance, the differential pressure Pdyn can be immediately determined from the detected magnitude of the capacitance C1, and further, the differential pressure Pdyn is determined. For example, the flow velocity Vf can be obtained by calculating using the above-described equation of the flow velocity Vf, or by using a table of the relationship between the flow velocity Vf and the differential pressure Pdyn in advance.

Next, the flow of the fluid is reversed, that is,
In FIG. 2, the case where the direction is indicated by a two-dot chain line will be described. In this case, contrary to the case described above, the second
Of the second sensor section communication path 21a in the sensor section 4 of FIG.
The opening of 21b faces the flow. Therefore, basically, as described above, the total pressure Ptot is generated in the second measurement concave portion 11, and the static pressure Pstat is generated in the vicinity of the diaphragm 13b outside the capacitance type micro flow sensor.

Therefore, the capacitance C2 of the second capacitor 26 according to the differential pressure Pdyn is detected, and the capacitance C2 is detected in the same manner as described above for the capacitance C1.
The flow velocity Vf can be known based on the detection result of.

Next, an example of a detection circuit for detecting the capacitances C1, C2 of the above-mentioned capacitance type micro flow sensor will be described with reference to FIG. This detection circuit
In the case of detecting the flow velocity in the opposite direction as described above for one capacitance output by the above-described capacitance type micro flow sensor, another similar circuit is required.

This detection circuit comprises a so-called diode bridge 3 comprising first to fourth diodes 31a to 31d.
0, and the capacitance C1 of the diode bridge 30 by the capacitance type micro flow sensor is provided.
(Or C2) and the external second to fourth capacitors 32
AC signal (Esinω)
t) is applied. That is, the portion surrounded by the two-dot chain line in FIG. 3 is the first sensor unit 3 (or the second sensor unit 4) of the capacitance type micro flow sensor, and one end thereof is connected to the first and second sensors. And the other end is connected to the ground and connected to one end of an external second capacitor 32a having a predetermined capacitance Cs. The other end is a third and fourth diode 3
It is connected to the connection point of 1c and 31d.

The external third and external capacitors 32b and 32c are connected in series, and are connected in parallel to the first and second diodes 31a and 31b.
External third capacitor 32b and external fourth capacitor 3
An AC signal (Esinωt) is applied between the connection point 2c and the ground. On the subsequent stage of the diode bridge 30, there is provided a so-called differential amplifier circuit 33 centered on an operational amplifier 34. As will be described later, a capacitance type micro flow sensor via the diode bridge 30 is provided. A voltage signal corresponding to the ratio between the capacitance C1 and the capacitance Cs of the external second capacitor 32a is differentially amplified and output.

That is, the cathode of the third diode 31c is connected to the inverting input terminal of the operational amplifier 34 via the fifth and first resistors 35e and 35a.
The anode of 1d is connected to the sixth and third resistors 35f, 35f.
c, each is connected to a non-inverting input terminal of the operational amplifier 34. The fifth and first resistors 35
e, 35a between the mutual connection point and the ground and between the sixth and third resistors 35f and 35c between the mutual connection point and the ground, a so-called first noise removing capacitor 36a for removing noise. 2 noise removal capacitor 36b
Are connected respectively.

A second resistor 35b as a so-called feedback resistor is connected between the output terminal and the inverting input terminal of the operational amplifier 34.
The fourth resistor 3 is connected between the non-inverting input terminal of
5d is connected.

Next, the operation in this configuration will be described. First, it is assumed that the capacitance value of the external second capacitor 32a is set equal to the capacitance value C1 when the flow velocity is zero. Also, the first and third resistors 35a, 3
It is assumed that the resistance values of 5c and 5c are equal, and the resistance values of the second and fourth resistors 35b and 35d are equal. Under these preconditions, when the flow rate is zero, the voltage on the cathode side of the third diode 31c and the fourth diode 31c
Since the voltage on the anode side of d becomes equal, the differential output from the operational amplifier 34 becomes zero.

On the other hand, when a flow velocity of a certain magnitude occurs, the capacitance C1 changes to a value corresponding to the magnitude of the flow velocity, so that the ratio to the capacitance C2 changes. Therefore, the voltage between the cathode of the third diode 31c and the anode of the fourth diode 31d changes, and the operational amplifier 3
As a result, the operational amplifier 34 obtains a differential output voltage corresponding to the magnitude of the flow velocity. Therefore, the flow velocity and the operational amplifier 3
4 has been examined, the operational amplifier 34
, It is possible to immediately know the flow rate detected by the capacitance type micro flow sensor.

Next, an example of a capacitance type micro flow sensor having a reference capacitor and a guard ring electrode will be described with reference to FIG. This example is characterized in that it has a reference electrode 53 as described later and that a so-called guard ring is provided. Less than,
Specifically, first, the example shown in FIG. 4 is for one-way flow velocity measurement. Then, for example, a first substrate 40 made of glass is joined to a second substrate 41 made of a semiconductor member such as silicon. On the second substrate 41 side, the measurement recess 42 and the measurement recess 42 are formed. The two communication passages 43a and 43b are formed to connect the diaphragm 4 with the outside.
The point 4 is basically the same as the capacitance type micro flow sensor shown in FIG.

A boss portion 45 is formed substantially at the center of the measurement concave portion 42. The thickness of the boss portion 45 (FIG. 4)
1 is also set to a size where a predetermined gap (for example, about several tens of microns) is formed between the detection electrode 49 of the first substrate 40 and the detection electrode 49 of the first substrate 40. It is. On the other hand, the second substrate 41 around the measurement concave portion 42
A contact avoiding step 46 is formed in the plane portion so as to surround the measurement concave portion 42 so that a predetermined gap is formed between the contact avoiding step 46 and the opposing surface of the first substrate 40.
This is for avoiding contact between the reference electrode 53 and the guard ring electrode 54 provided on the first substrate 40 and the silicon portion of the second substrate 41.

The vicinity of the end of the second substrate 41 in the short axis direction of one of the communication paths 43a is connected to a first substrate 40 described later.
The connection portions 52, 57, 59, and 61 provided in the first portion are notched, so that the connection portion cutout portions 47 are formed. An oxide film 48 is formed on the surface of the second substrate 41 around the contact avoiding step 46, and the detection electrode disposed on the first substrate 40 is formed on this surface. Even if the lead-out wiring 51 and the like come into contact, it is electrically insulated.

On the first substrate 40, a detection area formed by using, for example, ITO, at a position corresponding to the boss part 45 of the second substrate 41, in a rectangular shape having substantially the same area as the plane part of the boss part 45. An electrode 49 is provided, and the detection electrode 49 and the boss portion 45 constitute a so-called flat detection capacitor 50. One end of the detection electrode lead-out wiring 51 is connected to a corner of the detection electrode 49 near one of the communication paths 43a.

The detection electrode lead-out line 51 is protruded from one corner of the detection electrode 49, and is just one of the communication passages 43a.
And extends to a portion of the first substrate 40 facing substantially near the center of the communication passage 43a.
The notch 47 for the connecting portion is formed substantially at a right angle in front of the vicinity of the end portion a.
And is disposed substantially linearly therefrom in the vicinity of the notch 47 for the connection portion, and is substantially perpendicular to the side of the first substrate 40 in the vicinity of the notch 47 for the connection portion. After being bent to the side and being disposed in a linear shape with an appropriate length, it is further bent at a substantially right angle in the direction of the notch portion 47 for the connection portion, and is disposed with an appropriate length, and the end portion is provided. , Are connected to the detection electrode connection portion 52 formed in a substantially square shape.

On the other hand, the first part opposing the contact avoiding step 46
In the plane portion of the substrate 40, a reference electrode 53 and a guard ring electrode 54, which are formed in a strip shape, are arranged at appropriate intervals in a parallel state in a substantially similar shape to the plane shape of the contact avoidance step 46. In addition, the reference electrode 53 is disposed so as to be on the measurement concave portion 42 side, and the guard ring electrode 54 is disposed outside the reference electrode 53. Here, the reference electrode 5
In No. 3, the thickness, length, and the like are set such that the total area of the portion facing the contact avoidance step 46 is the same as the area of the detection electrode 49 described above. That is, the reference electrode 5
A reference capacitor 55 having a predetermined value C _REF is configured by a portion where the step 3 and the contact avoidance step 46 oppose each other. Then, by setting the total area of the reference electrode 53 as described above, the capacitance C _REF is made equal to the capacitance C 1 at zero flow velocity due to the opposition between the detection electrode 49 and the boss 45. I can do it. The reason why the capacitance of the reference capacitor 55 is set in this way is to improve the accuracy of the flow velocity detection by the detection circuit, as described later.

From one end of the reference electrode 53, that is, one end located on the side of the connection notch 47, a reference electrode lead-out wire 56 formed in a strip shape extends toward the connection notch 47. A connection portion for a reference electrode 57 for connection with an external circuit provided adjacent to the connection portion 52 for the detection electrode is connected to an end portion thereof.

The guard ring electrode 54 is for suppressing the generation of a so-called stray capacitance due to the distribution of the lines of electric force at the end of the reference electrode 53. That is, the guard ring electrode 54 is provided outside the reference electrode 53,
The reference electrode 53 is arranged in substantially the same arrangement shape, and is formed in a band shape in the direction of the connection notch 47 from one end, that is, just before the one end located on the connection notch 47 side. The extended lead ring 58 for the guard ring electrode is extended. A guard ring electrode connecting portion 59 provided adjacent to the reference electrode connecting portion 57 is connected to an end of the guard ring electrode lead wire 58.

The connection portion 59 for guard ring electrode is connected to an external circuit (not shown), and a predetermined potential is applied. By holding the guard ring electrode 54 at this predetermined voltage, reference is made. The line of electric force between the electrode 53 and the contact avoiding step 46 is linear, and the line of electric force is bent outward at the end of the reference electrode 53 as in the related art, so-called floating between itself and the outside. The generation of the capacitance suppresses the unstable capacitance value.

On the other hand, the back surface of the second substrate 41, that is,
On the surface opposite to the bonding surface with the first substrate 40, a rectangular boss electrode 62 is formed at a position corresponding to a substantially central portion of the boss 45, and a notch for connection is formed. A boss connection 61 is formed at an end near the 47 and near the guard ring connection 59. The boss portion electrode 62 and the boss portion connection portion 61 are connected to each other by a boss portion lead-out wire 60 appropriately disposed between the boss portion electrode 62 and the boss portion connection portion 61.
5 can be connected to the outside.

Next, a description will be given of a method of use, operation, and the like of the electrostatic micro flow sensor having the above configuration. First, since the reference capacitor 55 is a so-called fixed capacitor, its capacitance C _REF is also a fixed value. The initial value is set to a value in a state where the flow velocity is zero and no differential pressure acts on the diaphragm 44. As the detection circuit of this electrostatic micro flow sensor, the detection circuit previously shown in FIG. 3 is used.
Used as an alternative to a. That is, the reference electrode connecting portion 57 is connected to the third and fourth diodes 31c, 3c.
Connected to 1d connection point.

As described above, the reference capacitor 55 is used as a substitute for the external second capacitor 32a in FIG.
In other words, this is to improve the measurement accuracy of the flow velocity. That is, conventionally, as the external second capacitor 32a,
Since the capacitance of the capacitor C1 is different from that of the capacitor C1, if the value of the capacitor C1 changes due to temperature or the like, the capacitance of the external second capacitor 32a varies according to the capacitance C1.
It was different from that of 1. Therefore, the ratio between the capacitance C1 and the capacitance C2 changes, and the differential pressure P
There is a drawback that the original output voltage corresponding to dyn cannot be obtained from the operational amplifier 34, and the accuracy of the flow velocity value as the measurement result decreases. For this reason, in order to ensure a desired measurement accuracy of the flow velocity, a so-called compensation circuit for compensating for an error in the output voltage caused by a change in the ratio of the two capacitances described above is required. Was.

However, since the reference capacitor 55 has basically the same electrical characteristics as the capacitance C1, the variation of the capacitance value is also substantially the same as that of the capacitance C1. Even if the capacitance of the detection capacitor 50 and the reference capacitor 55 changes in temperature, the ratio between the two becomes substantially constant, and the above-described disadvantage is eliminated.

On the other hand, a predetermined voltage from outside is applied to the connection portion 59 for the guard ring electrode. Leakage can be eliminated, so-called stray capacitance can be suppressed, and the capacitance value of the reference capacitor 55 can be maintained at a predetermined value.

Under these preconditions, the operation of the capacitance type micro flow sensor itself in detecting the flow velocity is basically the same as the example shown in FIG. 1, so that it will be generally described first. The capacitance type micro flow sensor is arranged such that the entrances of the communication paths 43a and 43b face the flow of the fluid. Then, in the measurement concave portion 42, the diaphragm 44 has a total pressure Ptot and a static pressure Ps.
The differential pressure Pdyn, which is the difference from tat, acts, and the boss portion 45 is displaced in accordance with the differential pressure Pdyn, so that the differential pressure Pdyn is detected as a change in the capacitance C1.

On the other hand, between the differential pressure Pdyn (= Ptot-Pstat) and the flow velocity Vf, Vf = α × (P
tot−Pstat) ^1/2 holds, so that the relationship between the flow velocity Vf, the differential pressure Pdyn, and the capacitance C1 can be checked in advance to find the flow velocity Vf from the magnitude of the capacitance C1. it can. Here, the capacitance C1 is actually converted into a voltage by a detection circuit as shown in FIG. 3, and a change in the capacitance C1 is detected as a voltage change. After all, the flow velocity can be known from the voltage value. Note that the configuration and operation of the detection circuit shown in FIG. 3 are as described above, and thus, the description thereof will not be repeated here.

In the above-described capacitance type micro flow sensor, the reference electrode 53 and the guard ring electrode 5 are used.
4 has been described as being provided together, but for example, only the reference electrode 53 may be provided. In this case, there is a fear that the so-called stray capacitance of the reference capacitor 55 may be caused due to the absence of the guard ring electrode 54. Not a thing.

Next, as shown in FIG. 1 and FIG. 4, a capacitance type micro flow sensor which can be called a two-layer type in which two flat substrates, a glass substrate and a silicon substrate, are joined. An example of the manufacturing procedure will be described with reference to a comparatively simplified two-layer capacitance type micro flow sensor shown in FIG. First, the configuration of the capacitance type micro flow sensor will be described with reference to FIGS. In FIG. 5, for convenience,
As shown, three-dimensional coordinates based on x, y, and z axes are defined.

The capacitance type micro flow sensor shown in FIG. 5 is for detecting the flow velocity in one direction.
Basically, it has a configuration similar to that shown in FIG. That is, this capacitance-type micro flow sensor is made of an insulating member, for example,
And a second substrate 71 made of a semiconductor member, for example, silicon. The first substrate 70 and the second substrate 71 are joined together.

The second substrate 71 is provided with a measurement concave portion 72 having a frame-like outer edge in the xy plane. The bottom of the measurement recess 72 is formed into a thin film-shaped diaphragm 73 by etching the measurement recess 72 to an appropriate depth. The circumference of the measurement concave portion 72 is set to the same thickness (thickness in the z-axis direction).
And is a bonding surface with the first substrate 70. On the other hand, a portion surrounded by the measurement concave portion 72 is a boss portion 74.
When the first substrate 70 and the second substrate 71 are bonded to each other, the boss 74 just
The thickness in the z-axis direction is set so as to oppose the detection electrode 78 provided at a predetermined distance (for example, about several tens of microns).

A communication passage 75a is provided between the measurement recess 72 and one end of the second substrate 71 in the longitudinal axis direction (x-axis direction) to make the measurement recess 72 communicate with the outside. ,
75b are formed at appropriate intervals. The corner of the second substrate 71 near one of the communication paths 75a has its x
The y-plane shape is cut out in a rectangular shape to form a cutout portion 76, and the detection electrode connection portion 81 provided at a corresponding portion of the first substrate 70 does not contact the second substrate 71. Thus, connection with an external circuit is possible.

Further, the notch 76 communicates with one of the communication passages 75a between the notch 76 and one of the communication passages 75a and to one end of the second substrate 71. As a result, a lead-out wiring avoiding step 77 having a relatively small step is formed. In the lead wiring avoiding step 77, a part of the detection electrode lead wiring 80 passing through the portion of the first substrate 70 corresponding to the position of the lead wiring avoiding step 77 does not contact the second substrate 71. Thus, a predetermined gap is formed with the second substrate 71.

On the other hand, a detection electrode 78 made of, for example, ITO is provided on the first substrate 70 at a position corresponding to the boss 74 of the second substrate 71.
The detection capacitor 79 is constituted by 8 and the boss 74. From one corner of the detection electrode 78, a detection electrode lead wire 80 extends in the direction of one of the communication passages 75a.
5a, the first substrate 70 extends to the vicinity of one end of the first substrate 70, and is bent almost perpendicularly to the side of the lead wiring avoiding step 77 near the leading lead avoiding step 77, and this detection is performed. The other end of the electrode lead wire 80 is connected to the first substrate 7
0 is connected to a connection portion 81 for a detection electrode provided at one corner.

The principle of detecting the flow velocity in the above configuration is basically the same as that shown in FIG. 1, so that only a general description will be given here. When this capacitance type micro flow sensor is installed in a fluid such that the openings of the communication passages 75a and 75b face the flow of the fluid,
The pressure of the fluid in the measurement concave portion 72 becomes the total pressure Ptot, while the static pressure P near the diaphragm 73 outside.
stat occurs.

As a result, the diaphragm 73 has the total pressure P
The differential pressure Pdyn, which is the difference between the tot and the static pressure Pstat, acts and is deflected according to the magnitude thereof. As a result, the gap between the boss 74 and the detection electrode 78 changes, and the capacitance changes. Becomes This change in capacitance depends on the magnitude of the differential pressure Pdyn, and further on the flow rate.
Then, in practice, the change in capacitance is obtained as a voltage signal using the detection circuit as shown in FIG.
The flow velocity can be known from the voltage value.

Next, a first example of a manufacturing procedure of the capacitance type micro flow sensor having the above configuration will be described with reference to FIG.
This will be described with reference to FIGS. FIG.
(A) to FIG. 12 (B) schematically show a manufacturing state at an end face when this capacitance type micro flow sensor is cut in the z-axis direction along the line BB shown in FIG. This is shown in FIG. First, the procedure for manufacturing the second substrate 71 will be described with reference to FIGS. 7A and 9C. At first,
By so-called wafer dicing, for example, a silicon wafer 90 of 20 mm square (the size in the xy plane in FIG. 5) is obtained for the second substrate 71 (see FIG. 7A). Next, wafer cleaning is performed, and thereafter, an oxide film 91 having a predetermined thickness is formed on both surfaces of the silicon wafer 90 by thermal oxidation.
a, 91b are formed (see FIG. 7B).

Next, on the surfaces of both oxide films 91a and 91b,
Negative resists 92a and 92b are applied and fixed, respectively (see FIG. 7C). After that, using a mask (not shown), exposure, development, and the like are performed by a so-called photolithography method (hereinafter, referred to as a “photolithography method”) to leave a negative resist 92 a corresponding to the portion to be the frame 82, and only a predetermined portion of the negative rest 92 a (See FIG. 7D). Next, the oxide film 91a where the negative resist 92a has been removed is removed by etching using the remaining negative resist 92a as a protective film (see FIG. 7E).

Subsequently, all the negative resists 92 on both sides are formed.
a, 92b are removed (see FIG. 7F). Here, the portion a from which the oxide film 91a has been removed is finally connected to the communication path 75.
a, 75b are formed, and the portion b from which the oxide film 91a is removed is finally the measurement concave portion 72 and the boss portion 7.
4 is a portion where it is formed.

Next, the portions a and b are dug down by a predetermined value (for example, 8.5 μm) by silicon etching (see FIG. 8A), and after the etching is completed, the oxide film is etched to form the oxide films 91a and 91a. All 91b are removed (see FIG. 8B). Here, in silicon etching, etching is performed at a desired depth by performing etching by measuring the time for an etching time determined by the depth of silicon digging. Next, after performing wafer cleaning, new oxide films 91c and 91d are formed again on both surfaces of the silicon wafer 90 by thermal oxidation (see FIG. 8C). After the new oxide films 91c and 91d are formed, new negative resists 92c and 92d are applied to both surfaces (see FIG. 8D).

Next, in order to leave predetermined portions of the negative resists 92c and 92d by using a mask (not shown), exposure, development and the like are performed by a so-called photolithography method to leave only predetermined portions of the negative resists 92c and 92d (FIG. 8 (E)). Here, the portion c where the negative resist 92c has been removed
Is a part that finally becomes the diaphragm 73. Subsequently, the oxide films 91c and 91d not covered with the negative resists 92c and 92d are removed by oxide film etching using the negative resists 92c and 92d as a protective film (see FIG. 8F).

Next, all the negative resists 92c, 92d
Is removed (see FIG. 9A), and silicon etching is performed using the oxide film 91c as a protective film to form the communication paths 75a and 75b.
Then, a measurement concave portion 72 is formed (see FIG. 9B). In addition,
In this case, the silicon wafer 9 by silicon etching
The depth of 0 is set to a desired depth by measuring the etching time. Finally, the second substrate 71 is completed by removing all the oxide films 91c and 91d by oxide film etching (see FIG. 9C).

Next, the procedure for manufacturing the first substrate 70 will be described with reference to FIGS. 10 (A) to 10 (F). First, the glass substrate 95 is washed (see FIG. 10A), and then a positive resist 96 is applied to one surface (FIG. 10A).
(B)). Then, using a mask (not shown), a predetermined portion, that is, a portion of the positive resist 96 other than the portion where the detection electrode lead-out line 80 and the detection electrode connection portion 81 (see FIG. 5) are disposed is left. To this end, exposure, development, and the like are performed by a so-called photolithography method to remove only predetermined portions of the positive resist 96 (see FIG. 10C).

Next, Ti (titanium) and then Pt (platinum) are vapor-deposited on the entire surface of one surface to a predetermined thickness, respectively, to form a Ti / Pt film 97 (FIG. 10). (D)). Here, each deposition thickness is, for example, T
Let i be about 700 angstroms and Pt be about 300 angstroms. Thereafter, by removing the portion of the Ti / Pt film 97 formed on the positive resist 96 by so-called lift-off (see FIG. 10E), the lead-out wiring 80 for the detection electrode and the connection portion for the detection electrode are removed. 81 (not shown in FIG. 10E) will be formed.

Next, a new positive resist 96a is applied again on the entire surface of the one surface (see FIG. 10F).
Using a mask (not shown), exposure, development, and the like are performed by a so-called photolithography method to remove a predetermined portion of the positive resist 96a, thereby removing the predetermined portion of the positive resist 96a (see FIG. 11A). The portion d where the positive resist 96a is removed is a portion where the detection electrode 78 is provided.

Next, ITO is deposited on the entire one surface by sputtering to form an ITO film 98 (see FIG. 11B). Thereafter, only the portion of the ITO film 98 laminated on the positive resist 96a is removed by so-called lift-off, whereby the detection electrode 78 is completed (see FIG. 11C). After lift-off, for example, ultrasonic cleaning is performed using acetone.

Next, a procedure for joining the first substrate 70 and the second substrate 71 will be described with reference to FIGS. One surface of the second substrate 71, that is,
The first substrate 70 is provided on the surface on which the measurement concave portion 72 and the like are formed.
Are mounted, the two are joined by anodic bonding (see FIG. 12A). Next, aluminum is deposited in a predetermined shape on a suitable portion of the second substrate 71 by sputtering, and is subjected to so-called sintering to form a ground electrode (not shown). Finally, a connection wire 99 for connecting the detection electrode connection portion 81 to an external circuit (not shown) is connected to the detection electrode connection portion 81 by so-called wire bonding (see FIG. 12B).

Next, an example of a capacitance type micro flow sensor having a three-layer structure will be described with reference to FIGS. In FIG. 13, for convenience, three-dimensional coordinates based on x, y, and z axes are defined as illustrated. This capacitance type micro flow sensor includes a first glass substrate 111 made of, for example, glass as an insulating member, and a second glass substrate 1 made of glass as well.
12, the semiconductor members are joined to each other so as to sandwich a central substrate 110 made of, for example, silicon as a semiconductor member.

The central substrate 110 has a main measuring concave portion 113 and a sub-measuring concave portion 114 basically similar to the measuring concave portion 72 in the example of FIG. And FIG. 15). That is, on the plane of the central substrate 110 facing the first glass substrate 111, the main measurement recess 113 is formed in a frame shape near the approximate center thereof, and the main boss portion 1 is surrounded by the main measurement recess 113.
15 are formed. A sub-measuring recess 114 having substantially the same shape and dimensions as the main measurement recess 113 is provided at a position corresponding to the main measurement recess 113 on the flat side of the central substrate 110 opposite to the side where the main measurement recess 113 is provided. (See FIG. 15). A sub-boss 116 is formed so as to be surrounded by the sub-measurement recess 114, and the surface of the sub-boss 116 on the opposite side is the main boss 115.
(See FIGS. 13 and 15).

Main measurement recess 113 and sub measurement recess 114
Are both formed by silicon etching.
For example, at the time of the silicon etching, by appropriately adjusting the etching time, the bottoms of the main measurement concave portion 113 and the sub-measurement concave portion 114 are formed in a thin film shape and the diaphragm 1 is formed.
17 (see FIGS. 13 and 15).

On the other hand, the main measurement recess 113 of the central substrate 110
On the side provided with the two communication paths 118a, 1
18b is the short axis direction (y-axis direction) of the main measurement recess 113.
One end is open to the outside at an appropriate interval, and the other end is in the longitudinal axis direction (x-axis direction) of the main measurement recess 113.
(See FIG. 13).
reference).

Further, the first and second substrates 111 and 122
In addition, at one end of the central substrate 110, that is, in this case, at one end of the first and second substrates 111 and 122 and the central substrate 110 in the longitudinal axis direction (y-axis direction), First and second connection-portion cutouts 119 and 120 formed by removing silicon so as to have a rectangular shape in the xy plane are formed at predetermined intervals (see FIG. 13). That is, the first connection portion cutout portion 119 is formed by removing silicon such that its xy plane shape is rectangular in the vicinity of one corner of one end of the central substrate 110 in the longitudinal axis direction. Central board side notch 1
19a and a second substrate-side cutout 119b similarly formed in a corresponding portion of the second substrate 112.

On the other hand, the second connection notch 120
Is a second central substrate side notch formed similarly to the first central substrate side notch 119a at an appropriate distance in the x-axis direction from the first central substrate side notch 119a. 120a and a first substrate side cutout 120b similarly formed in a corresponding portion of the first substrate 111 (see FIG. 13). In the first and second cutouts 119 and 120 for the connection portion, the main electrode connection portion 128 and the sub-electrode connection portion 132 provided on the first and second glass substrates 111 and 112 are exactly located. And connection portions 128 and 132 for the main and sub-electrodes.
Are notched portions 119 and 120 for the first and second connection portions.
Thereby, it does not come into contact with the central substrate 110.

Further, a recess 121 for avoiding main electrode wiring is formed relatively shallow between one of the communication passages 118a and the first cutout portion 119 for the connection portion so as to communicate with both. See FIG. 13). This main electrode wiring avoiding recess 12
Numeral 1 is provided at the same position as the main electrode lead wire 127 provided on the first glass substrate 111 so that the main electrode lead wire 127 does not contact the central substrate 110.

As described above, the surface of the central substrate 110 which is to be joined to the second glass substrate 112 is located at a position corresponding to the main measurement recess 113 and the main boss 115.
The sub-measurement concave portion 114 and the sub-boss portion 116 are similarly formed, and a sub-electrode wiring avoidance is provided between the sub-boss portion 116 and the second connection portion cutout portion 120 so as to connect them. The recess 122 is relatively shallowly recessed (FIG. 1).
5). The sub-electrode wiring avoiding recess 122 is provided with the sub-electrode lead-out wiring 1 provided on the second
31 is located at the same position as the sub-electrode 31, so that the sub-electrode lead-out line 131 does not contact the central substrate 110.

On the other hand, one surface of the first glass substrate 111, that is, the surface to be joined to the central substrate 110, is formed of, for example, ITO at a position corresponding to the main boss 115 provided on the central substrate 110. The main detection electrode 125 is provided with substantially the same planar shape and dimensions as the main boss 115 (see FIG. 13). The main detection electrode 125 and the main boss 115 form a so-called flat main capacitor 126. In addition, from one corner of the main detection electrode 125, for example, in this example, from the corner closest to the one communication passage 118a, the main electrode lead-out line 127 made of a conductive member is similarly conductive as follows. It extends to the main electrode connecting portion 128 made of a member. In other words, the main electrode lead-out line 127 extends along one of the communication passages 118a, and is bent at a substantially right angle in the middle of the communication passage 118a in the direction of the first connection-portion notch 119, so that the main electrode connection It extends to the portion 128 (see FIG. 13).

On one surface of the second glass substrate 112, that is, the surface to be joined to the central substrate 110, the conductive member is placed at a position corresponding to the sub-boss 116 provided on the central substrate 110. The sub-detection electrode 129 is provided with substantially the same planar shape and dimensions as the sub-boss 116.
The sub-detecting electrode 129 and the sub-boss portion 116 form a so-called flat plate-shaped reference capacitor 130. In addition, from one corner of the sub-detection electrode 129, for example, in this example, the corner closest to the second connection portion cutout 120 described above, a sub-electrode lead made of a conductive material is used. The wiring 131 extends to the sub-electrode connection 132 as follows. That is,
The lead-out line 131 for the sub-electrode extends a predetermined length in the direction opposite to the sub-detection electrode 129 along the x-axis direction,
Therefore, it is bent at a right angle in the direction of the sub-electrode connecting portion 132 made of a conductive member and extended to the sub-electrode connecting portion 132.

In the second glass substrate 112, the vicinity of one end of the sub-detection electrode 129, that is,
In this example, the static pressure introduction hole 1 is provided near the end on the side having the corner where the sub electrode lead-out line 131 extends.
29 are drilled in the z-axis direction (see FIGS. 13 and 16). That is, the static pressure introduction hole 129 is formed such that one of its openings is the central substrate 1 on the side facing the second glass substrate 112.
The other opening is formed so as to gradually open from the other opening toward one opening so as to face the tenth diaphragm 117 and the other opening is opened to the outside of the second glass substrate 112. (See FIG. 16).

The thicknesses (thicknesses in the z-axis direction) of the first and second glass substrates 111 and 112 and the central substrate 110 are shown as substantially the same in FIG. 13 for convenience. In practice, for example, the central substrate 11
The thickness of the first and second glass substrates 111 and 112 is preferably set to about 1 mm while the thickness of 0 is about 0.3 mm. On the other hand, in FIG.
Contrary to the case of FIG. 13, the first and second glass substrates 11
1, 112 and the thickness of the central substrate 110 are relatively shown.

Next, the operation in the above configuration will be described with reference to FIG.
This will be described with reference to FIGS. First, this capacitance type micro flow sensor uses a differential pressure P generated by a fluid.
The point that dyn is detected as a change in the capacitance C1 of the main capacitor 126 is basically the same as in the examples shown in FIGS.

That is, in detecting the flow velocity, the capacitance type micro flow sensor is arranged in the fluid such that the openings of the communication passages 118a and 118b to the outside face the flow of the fluid. If the fluid flows at a certain flow velocity as shown by the arrow, a so-called stagnation point is generated near the opening of the communication passages 118a and 118b to the outside (see FIG. 16). The pressure is the so-called total pressure Ptot. The pressure of the fluid in the main measurement concave portion 113 also becomes the total pressure Ptot.

On the other hand, the first and second glass substrates 111 and 11 are located outside the capacitance type micro flow sensor.
The pressure near the plane 2 is the static pressure Pstat. The sub-measuring recess 114 is in communication with the outside in a static pressure state through the static pressure introducing hole 129, so that the sub-measuring recess 1
The pressure inside 14 also becomes the static pressure Pstat. As a result, a differential pressure Pdyn, which is the difference between the total pressure Ptot and the static pressure Pstat, is applied to the diaphragm 117, and the diaphragm 117 is moved to the main measurement recess 113.
It acts so as to press from the side to the sub-measurement recess 114 side.
As a result, as the diaphragm 117 bends from the main measurement recess 113 to the sub measurement recess 114, the main detection electrode 12
5 and the main boss 115 are enlarged to reduce the capacitance of the main capacitor 126, while the distance between the sub-detection electrode 129 and the sub-boss 116 is reduced, and the reference capacitor 1
30 will be increased.

The differential pressure Pdyn can be basically regarded as a change in the capacitance C1 of the main capacitor 126. More practically, the differential pressure Pdyn is obtained by a detection circuit described later. Can be detected as Then, between the fluid flow velocity Vf and the differential pressure Pdyn, the flow velocity Vf = α × (Ptot
−Pstat) Since there is a relationship of ^1/2 (where α = (2 / ρ) ^1/2 and ρ is the density of the fluid), detection is performed by checking the relationship between the differential pressure Pdyn and the flow velocity in advance. The flow velocity can be known based on the voltage value of the circuit.

As described above, in the capacitance type micro flow sensor in this example, since the stagnation point is substantially located at the opening to the outside of the communication holes 118a and 118b, as shown in FIG. The detection error is smaller than that of the so-called two-layer type shown in FIGS. That is, conventionally, for example, in a so-called two-layer capacitive microflow sensor as shown in FIGS. 1, 4 and 5, a substrate made of silicon (in FIG. 1, the second substrate 2 is In FIG. 4, the second substrate 41 corresponds to the other glass substrate (in FIG. 1, the first substrate 41 corresponds to the first substrate).
Substrate 1 is thinner than that of the first substrate 40 in FIG. 4), and if the thickness of the substrate made of silicon is relatively 1, the other glass substrate is approximately It is set to about three times.

On the other hand, the stagnation point occurs substantially at an intermediate point with respect to the entire thickness of the capacitance type micro flow sensor, that is, for example, in the example of FIG. In a conventional so-called two-layer type plate having a thickness, the stagnation point is, in the example of FIG. 1, from the opening of the first communication passages 16 a and 16 b to the outside. Is rather generated at a position shifted toward the first substrate 1 side. Therefore, a detection error occurs and the detection accuracy is not so high.

On the other hand, the three-layer capacitance type micro flow sensor as described above uses the communication paths 118a, 1
As described above, the stagnation point is caused by the communication path since the central substrate 110 having the 18b is sandwiched between the first and second glass substrates 111 and 112 having substantially the same plate thickness. It occurs near the openings of the 118a and 118b to the outside, so that the detection error is smaller than that of a conventional so-called two-layer capacitance type micro flow sensor.

On the other hand, the reference capacitor 130 is used to suppress an error in the detection circuit. That is,
In the case of the detection circuit previously shown in FIG. 3, the external second capacitor 32a is configured to use a capacitor as a so-called normal electronic component separate from the capacitance type micro flow sensor. In this case, since the electrical characteristics are different from those of the capacitor of the capacitance type micro flow sensor, an imbalance occurs between the potential on the cathode side of the third diode 31c and the potential on the anode side of the fourth diode 31d. Therefore, the differential pressure Pdyn
However, there is a disadvantage that an original output voltage corresponding to the above cannot be obtained. Therefore, in the detection circuit shown in FIG. 3, if the error of the output voltage exceeds the desired detection accuracy, it is necessary to suppress the error by adding a so-called compensation circuit.

Therefore, the reference capacitor 130 in the capacitance type micro flow sensor is provided to solve such a drawback. That is, as the detection circuit of the capacitance type micro flow sensor, for example, a configuration as shown in FIG. 17 is suitable. Hereinafter, the configuration and operation of the detection circuit will be described with reference to FIG. 17 together with the function of the reference capacitor 130. The same components as those of the detection circuit shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted. Hereinafter, different points will be mainly described.

In FIG. 17, the portion surrounded by the two-dot chain line is the portion of the three-layer capacitance type micro flow sensor, the portion of the capacitance C1 is the main capacitor 126, and The capacitance C _REF is the reference capacitor 1
30. That is, the main electrode connecting portion 128 is
At the connection point between the second and third diodes 31a and 31b, the sub-electrode connecting portion 132 is connected to the third and fourth diodes 31a and 31b.
Connected to the connection points of c and 31d, respectively. In addition, the central substrate 110 is connected to the ground at an appropriate location (not shown), so that in FIG.
6 is equivalent to a point where the connection point between the reference capacitor 130 and the reference capacitor 130 is connected to the ground.

For easy understanding, for example, it is assumed that the initial values of the main condenser 126 and the reference condenser 130, that is, the capacitances when the flow velocity is zero are the same, and when the flow velocity is zero, , The third diode 31
The circuit operation will be described on the assumption that the circuit constant is set such that the potential on the cathode side of c is the same as the potential on the anode side of the fourth diode 31d. Under these preconditions, when the flow velocity is zero, the output voltage of the operational amplifier 34 is also zero.

Next, assuming that a certain flow velocity occurs, the capacitance of the main condenser 126 decreases from an initial value according to the differential pressure Pdyn, in other words, according to the flow velocity, while the capacitance of the reference condenser 130 decreases. The capacitance is increased from the initial value according to the flow velocity. Therefore, the third
The potential on the cathode side of the diode 31c is larger than the potential on the anode side of the fourth diode 31d, and the magnitude thereof is in accordance with the differential pressure Pdyn. And
The operational amplifier 34 outputs a differentially amplified voltage between the cathode of the third diode 31c and the anode of the fourth diode 31d.

The output voltage of the operational amplifier 34 is the differential pressure Pdyn
And between the flow velocity Vf and the differential pressure Pdyn,
As described above, since there is a relationship of Vf = α × (Ptot−Pstat) ^1/2 , the output voltage of the operational amplifier 34 and the flow velocity V
By examining the relationship with f, the flow velocity Vf can be known from the output voltage of the operational amplifier 34.

Here, since the main capacitor 126 and the reference capacitor 130 have basically the same configuration, changes in electrical characteristics with respect to environmental changes such as temperature, for example, are substantially the same. Therefore, even if both capacitances change in temperature, the ratio between the two capacitances becomes substantially the same. On the other hand, in the past, since the electrical characteristics were not the same, the ratio of the capacitances changed, resulting in a decrease in the accuracy of the measurement results of the flow velocity. In the capacitance type micro flow sensor shown in FIG. 13, as described above, the ratio between the capacitance of the main capacitor 126 and the capacitance of the reference capacitor 130 becomes substantially constant. Even if the capacitance of the main capacitor 126 and the reference capacitor 130 changes, thereby changing the output voltage of the operational amplifier 34, the change is constant. Therefore, if the temperature characteristics of the output voltage are checked in advance, An accurate flow rate can be known from the temperature and the output voltage at the time of measurement, and a special compensation circuit for canceling an error in the output voltage is not required unlike the related art.

Next, an example in which a buffering projection is provided on the above-mentioned capacitance type micro flow sensor will be described with reference to FIG. In this example, a plurality of buffer projections 13 are provided on the surface of the main boss 115 and the surface of the sub-boss 116, respectively.
5 is provided. The buffer protrusion 135 is formed, for example, in a substantially hemispherical shape. The size of the protrusion from the surface of the main boss portion 115 and the size of the protrusion from the surface of the sub boss portion 116 are, for example, the main boss portion. 115 and main detection electrode 1
Assuming that the interval at the normal time with the distance 25 is about 10 microns, the distance is set to about 1 micron.

Incidentally, when a large impact force is applied to the whole of the capacitance type micro flow sensor from the outside for some reason or inserted into a sudden flow exceeding the measurement limit, the main boss portion 115 The entire planar portion collides with the main detection electrode 125 or the entire planar portion of the sub-boss portion 116 collides with the sub-detection electrode 129, and the central substrate 110
There is a fear that excessive stress may occur to cause breakage or cracking.

In the case where the buffer projection 135 is provided as described above, even if the large impact force as described above is applied to the capacitance type micro flow sensor or the like, the buffer projection 135 is used as the main detection electrode. 125 or sub-detection electrode 129
And the entire main boss portion 115 does not collide with the main detection electrode 125 or the entire sub-boss portion 116 does not collide with the sub-detection electrode 129. Will be suppressed.

The shape and number of the buffer projections 135, and furthermore, the interval between them is not limited to a specific shape or the like, and may be set arbitrarily. The buffer projection 135 as described above can be used not only for the three-layer capacitance type macro flow sensor shown in FIG. 13 but also for the capacitance type micro flow sensor shown in FIGS. 1, 4 and 5. Needless to say, the flow sensor may be provided similarly.

Next, application examples of the above-mentioned capacitance type micro flow sensor will be described with reference to FIGS. In this example, a capacitance type micro flow sensor is externally attached to the injector 140 so that the flow rate of fuel in the injector 140 used for a fuel injection device of an automobile engine can be measured. First, FIG.
9 will be described with reference to the schematic configuration diagram of FIG. 9. In the injector 140, a capacitance type micro flow sensor 145 is attached to the injector 140 so that the fuel injection speed can be detected. An external sensor fixture 150 is attached.

The external sensor fixture 150 includes, for example, a main fixture 151 attached to an end of the injector 140 on the fuel injection (not shown) side and a capacitance type micro flow sensor 145. Fuel passage 155 of fixture 151
And a sub fixture 152 for holding the flow rate in a detectable manner.

The output signal from the capacitance type micro flow sensor 145 is converted into a voltage signal by the detection circuit 141, and the output voltage is converted to a digital voltage system 14.
2 allows direct reading. Here, the detection circuit 14
Reference numeral 1 denotes an AC signal (Esin ω) necessary for the detection operation by the detection circuit 141, which has the configuration shown in FIGS.
t) is supplied from the signal generator 143. The power supply voltage required for the detection circuit 141 is supplied by the power supply circuit 144.

Next, a more specific configuration example of the external sensor fixture 150 will be described with reference to FIGS. The external sensor fixture 150 has a hollow cylindrical fuel passage 155 therein, and a cylindrical sub-fixture insertion hole 156 into which the sub-fixture 152 is fitted is formed in the fuel passage 155. The main fixture 151 is provided so as to be orthogonal to the main fixture 151, and the auxiliary fixture 152 is fixed to the main fixture 151 while holding the capacitance type micro flow sensor 145. (See FIGS. 20 and 23). FIG. 23 is a partial vertical cross-sectional view of the external sensor fixture 150.
Is shown in a detached state, and other portions are shown in cross sections.

In this example, the main fixture 151 is formed in a substantially columnar shape in its entirety, and one end of the main fixture 151 is fitted with an end of the injector 140 on the side of a fuel injection pump (not shown). An injector fitting hole 157 is formed, and the injector fitting hole 157 is formed in the fuel passage 15.
5 is connected. On the other hand, the other end of the main fixture 151 is formed with a pipe fitting hole 158 into which a connection pipe (not shown) for connecting to a fuel injection pump (not shown) is fitted. It communicates with the fuel passage 155 (see FIG. 23). In addition, the main fixture 151 is provided so as to be orthogonal to the fuel passage 155.
A cylindrical sub-fixture fitting insertion hole 156 into which a part of a sub-fixture 152 described later is fitted is formed (see FIG. 23).

The sub fixture 152 has a columnar fitting portion 165 formed in a column shape to be inserted into the sub fixture fitting insertion hole 156 of the main fixture 151, and a disc-shaped one end of the column fitting portion 165. The fixing flange 166 is formed, and the fixing flange 166 is screwed to the outer peripheral surface of the main fixture 151 (see FIGS. 20 and 21). The fixing flange 166 is provided with a plurality of wiring extraction holes 167 for extracting wiring (not shown) from the capacitance type micro flow sensor 145 to the outside at appropriate intervals (FIG. 20).

Further, a part of the column fitting portion 165 is detachable with a screw. That is, the column fitting portion 165 includes a main body 168 integrally formed with the fixing flange 166 and a sensor fixing piece 169 detachably attached to the main body 168 by a screw. The capacitance type micro flow sensor 145 is fixed between the main body 168 and the sensor fixing piece 169 (see FIG. 21).

The sensor fixing piece 169 is formed in a semi-cylindrical shape in its entirety. A first semi-cylindrical groove 170 having a semi-cylindrical shape is formed, and a second semi-cylindrical groove 170 similarly formed on the body portion 168 side is formed.
And a part of the fuel passage 155 of the main fixture 151 together with the semi-cylindrical groove 171. That is, in a state where the main fixing member 151 and the sub fixing member 152 are assembled as shown in FIG. Are formed so as to communicate with the fuel passage 155 of the main fixture 151 (see FIG. 23).

Further, the main body 16 of the sensor fixing piece 169
8, a capacitance type micro flow sensor 1
45, one-sided first fitting step portion 172 to which both side portions are fitted.
In addition, a fixed one-side second fitting step 173 is formed beside the first semi-cylindrical groove 170 so as to communicate with the first semi-cylindrical groove 170 (see FIG. 22). And the main body 16
Similarly, a first fitting step 174 on the main body side and a second fitting step 175 on the main body side are formed on the eighth side.
), The one side of the electrostatic capacity type micro flow sensor 145 is fixed to the fixed one side second fitting step portion 172 and the main body side first fitting step portion 174. The other side of the capacitance type micro flow sensor 145 is sandwiched between the fitting step 173 and the second fitting step 175 on the main body side.

It is to be noted that when the sensor fixing piece 169 is attached to the main body 168, the sensor fixing piece 169 is moved from an appropriate position of the fixing half-side second fitting step 173 toward an end located on the fixing flange 166 side. In addition, a wiring escape groove 176 for drawing out a wiring (not shown) from the capacitance type micro flow sensor 145 to the outside is recessed (see FIG. 22). On the other hand, a plurality of wiring escape holes 177 are formed at the center of the fixing flange 166 on the main body 168 side (see FIG. 21), and the electrostatic capacitance type drawn out through the wiring escape groove 176 earlier. The wiring from the micro flow sensor 145 is connected to the plurality of wiring lead holes 1 through the wiring escape holes 177.
It can be pulled out from the space 67 (see FIG. 20).

In FIG. 21, the capacitance type micro flow sensor 145 is simplified for simplicity.
5 may be any of those shown in FIG. 1, FIG. 4, FIG. 5, or FIG.

Regardless of which capacitance type micro flow sensor is used, what is common is that
When mounting the first and second semi-cylindrical grooves 170 and 171 in the direction perpendicular to the radial direction of the first and second semi-cylindrical grooves 170 and 171 (FIG. 21). At the front and back of the paper), in other words, the main fixture 1
When it is attached to 51, it is fixed between the main body 168 and the sensor fixing piece 169 so as to be in a direction along the fuel passage 155.

After the fixing to the sub fixture 152 is completed, the column fitting portion 165 of the sub fixture 152 is attached to the main fixture 15.
1 is inserted into the sub-fixture fitting insertion hole 156, and the communication hole (not shown) of the capacitance type micro flow sensor 145 is positioned so as to face the injector 140 side. 152 is fixed to the main fixture 151, and the external sensor fixture 150 is assembled.

[0118]

As described above, according to the first aspect of the present invention, since two sensors are provided integrally, the flow velocity can be measured in two directions. In the case of the configuration, it is possible to detect the flow velocity in the reverse direction,
It is possible to provide a capacitance-type micro flow sensor that is more practical than before.

According to the third aspect of the present invention, a fixed-value capacitor made of basically the same member as the capacitor for detecting the flow velocity is provided, and this can be used in the detection circuit. In the detection circuit, unlike the conventional case where the capacitor is combined with a capacitor having completely different electric characteristics, a detection circuit can be configured by a combination with a similar one having electric characteristics.
It is possible to suppress the influence on the output of the detection circuit due to a change in the ambient temperature or the like as compared with the related art, and to obtain a more reliable measurement result.

According to the fourth aspect of the present invention, the leakage of the electric flux lines from the second electrode can be suppressed, and in addition to the effect of the third aspect, the generation of so-called stray capacitance is suppressed. Therefore, a more reliable capacitance type micro flow sensor can be provided.

According to the fifth aspect of the invention, the so-called 3
A stagnation point is created at the opening of the communication passage leading to the inside of the capacitance type micro flow sensor by adopting a layer structure, so that the pressure inside the capacitance type micro flow sensor can be accurately measured unlike the conventional model. In this case, a so-called total pressure state can be attained, and more accurate flow velocity measurement can be performed, so that a highly reliable capacitance type micro flow sensor can be provided.

According to the sixth and seventh aspects of the invention, in addition to the effect of the fifth aspect, the projection is provided on the main boss portion or the sub boss portion, so that the entire plane portion of the main boss portion is main detected. The electrode, or the entire flat portion of the sub-boss portion is prevented from colliding with the sub-detection electrode, and the main boss portion and the sub-boss portion made of silicon that is vulnerable to impact can be protected.
The service life can be further extended as compared with the related art.

According to the eighth aspect of the present invention, since the size of the silicon digging is determined by the time of the silicon etching during the silicon etching, the size of the digging is adjusted relatively easily. And the manufacturing procedure can be simplified.

According to the ninth aspect of the present invention, the external fixture is provided on the injector by adopting a configuration in which the fuel flow rate can be easily measured by the capacitance type micro flow sensor in the existing fuel passage. Simply by attaching, the flow rate can be measured by the capacitance type micro flow sensor, and the existing fuel injection device can be easily attached without any other modification.

[Brief description of the drawings]

FIG. 1 is an overall perspective view showing an example of a configuration of a capacitance type micro flow sensor for measuring flow velocity in two directions in an exploded state.

FIG. 2 is a cross-sectional view when the capacitance type micro flow sensor is cut along the line AA in FIG.

FIG. 3 is a circuit diagram illustrating an example of a circuit configuration of a detection circuit.

FIG. 4 is an overall perspective view showing an example of a configuration of a capacitance type micro flow sensor having a reference electrode and a guard ring electrode in an exploded state.

FIG. 5 is an overall perspective view showing an example of a configuration of a two-layer capacitance type micro flow sensor in an exploded state.

6 is a plan view in the xy plane of the capacitance type micro flow sensor shown in FIG.

FIG. 7 is a view schematically showing a manufacturing procedure of the capacitance type micro flow sensor shown in FIG. 5, and is a schematic view showing a first half of a manufacturing procedure of the second substrate.

FIG. 8 is a view schematically showing a manufacturing procedure of the capacitance type micro flow sensor shown in FIG. 5, and is a schematic view showing a latter half of the manufacturing procedure of the second substrate.

FIG. 9 is a view schematically showing a manufacturing procedure of the capacitance type micro flow sensor shown in FIG. 5, and is a schematic view showing a latter half of the manufacturing procedure of the second substrate.

FIG. 10 is a view schematically showing a manufacturing procedure of the capacitance type micro flow sensor shown in FIG. 5, and is a schematic view showing a first half of a manufacturing procedure of the first substrate.

FIG. 11 is a view schematically showing a manufacturing procedure of the capacitance type micro flow sensor shown in FIG. 5, and is a schematic view showing a latter half of the manufacturing procedure of the first substrate.

FIG. 12 is a view schematically showing a manufacturing procedure of the capacitance type micro flow sensor shown in FIG.
FIG. 4 is a schematic view showing a bonding portion of a substrate.

FIG. 13 is an overall perspective view showing an example of a configuration of a three-layer capacitance type micro flow sensor in an exploded state.

FIG. 14 is a cross-sectional view when the center substrate is cut along the line CC of FIG. 13;

FIG. 15 is an overall perspective view when the central substrate is viewed from below.

FIG. 16 is a cross-sectional view of the capacitance type micro flow sensor cut along the line CC in FIG. 13;

17 is a circuit diagram showing an example of a circuit configuration of a detection circuit suitable for the capacitance type micro flow sensor shown in FIG.

FIG. 18 is a schematic view schematically showing an example of disposing a buffer projection.

FIG. 19 is a schematic configuration diagram in the case of using a capacitance type micro flow sensor for measuring the flow velocity of fuel in an injector for fuel injection.

FIG. 20 is an overall perspective view of an external fixing tool for externally attaching the electrostatic micro flow sensor to the injector.

21 is an exploded perspective view of a configuration example of a sub-fixing tool constituting the external fixing tool illustrated in FIG. 20;

FIG. 22 is a plan view of a sensor fixing piece used in the sub-fixing tool shown in FIG. 21 at a joint surface with a main body.

FIG. 23 is a partial longitudinal sectional view of the external fixture shown in FIG. 20;

[Explanation of symbols]

 5 First detection electrode 6 Second detection electrode 10 First measurement recess 11 Second measurement recess 13a, 13b Diaphragm 15 First boss 20 Second boss 42 Measurement Concave part 44 ... Diaphragm 45 ... Boss part 49 ... Detection electrode 53 ... Reference electrode 54 ... Guard ring electrode 115 ... Main boss part 116 ... Sub boss part 117 ... Diaphragm 125 ... Main detection electrode 129 ... Sub detection electrode 133 ... Static pressure introduction hole 151: Main fixture 152: Secondary fixture 165: Column fitting part 166: Fixing flange 169: Sensor fixing piece

Claims (9)

[Claims] 1. A first substrate made of an insulating member and a second substrate made of a semiconductor member are joined to each other, and a conductive surface of the first substrate facing the second substrate is electrically conductive. A first electrode and a second electrode, each of which is made of a conductive member, are respectively disposed, and a second substrate is opposed to the first electrode on a side facing the first substrate via a predetermined gap. A first boss portion and a second boss portion facing the second electrode with a predetermined gap therebetween are provided, and a first boss portion is provided around the first boss portion so that a bottom portion becomes a diaphragm. A first recess is provided around the second boss portion, and second recesses are respectively provided so that a bottom portion becomes a diaphragm, and a partition for separating the first recess from the second recess. Is formed between the first concave portion and the second concave portion, and further, the first concave portion and the second concave portion are formed. A first communication passage communicating with the second recess is formed, and a second communication passage communicating the second recess with the outside is formed. The pressure difference between the pressure in the first recess and the outside is reduced. A change in the capacitance of a first capacitor formed by the first electrode and the first main boss portion, and a change in the capacitance of the second capacitor formed by the second electrode and the second boss portion. A capacitance type micro flow sensor characterized in that a change in capacitance of the second capacitor can be detected. 2. The method according to claim 1, wherein the opening of the first communication passage to the outside and the opening of the second communication passage to the outside are formed so as to face in opposite directions, thereby enabling detection of the flow velocity in the opposite direction. The capacitance type micro flow sensor according to claim 1, wherein 3. A first substrate made of an insulating member and a second substrate made of a semiconductor member are joined to each other, and a conductive surface of the first substrate facing the second substrate is provided. While a first electrode made of a conductive member is provided, a boss portion facing the first electrode via a predetermined gap is provided on a side of the second substrate facing the first substrate. A recess is formed around the first boss portion so that a bottom portion becomes a diaphragm, and a communication passage communicating the recess with the outside is formed. A capacitance microflow sensor configured to be able to detect a change in capacitance of a capacitor formed by the electrode and the boss portion, which is generated according to a pressure difference between the electrode and the boss portion. A first plane portion facing the first plane portion; A second electrode is provided on a portion of the first substrate facing the plane portion, while the second electrode has an area which is formed to have a predetermined gap with the substrate. A predetermined capacitance which is set to be the same as that of the first electrode and which is generated between the first electrode and the flat portion formed around the concave portion; Capacitive micro flow sensor. And a flat portion formed around the concave portion so as to form a predetermined gap with the first substrate.
In addition, a third electrode is provided on the first substrate so as to surround the second electrode, and the third electrode is configured to be held at a predetermined potential outside and used as a guard ring. The capacitance type micro flow sensor according to claim 3, wherein: 5. A semiconductor device comprising: first and second substrates made of an insulating member; and a central substrate made of a semiconductor member.
And the first and second substrates and the central substrate are joined so that the central substrate is sandwiched between the first substrate and the second substrate. The surface of the first substrate facing the central substrate includes a conductive member. A main detection electrode is provided, and a sub-detection electrode made of a conductive member is provided on a surface of the second substrate facing the central substrate. The main substrate is opposed to the first substrate. A main boss portion facing the main detection electrode via a predetermined gap is provided on the surface, and a main measurement concave portion is formed around the main boss portion so that a bottom portion becomes a diaphragm. A communication passage communicating the main measurement concave portion and the outside is formed, and a sub boss portion facing the sub detection electrode at a predetermined interval is provided on a surface of the central substrate facing the second substrate. It is provided on the opposite side to the main boss, around this sub boss, And, on the opposite side of the main measurement recess, a sub measurement recess is provided in the same manner as the main measurement recess. On the second substrate, one opening is provided in the sub measurement recess and the other opening is provided. A static pressure introducing hole which is open to the outside is formed, and the electrostatic capacitance of a first capacitor formed by the main detection electrode and the main boss portion generated according to a pressure difference between the pressure in the main measurement recess and the outside. A change in capacitance and a change in capacitance of a second capacitor formed by the sub-detection electrode and the sub-boss portion are configured to be detectable, respectively. . 6. The electrostatic device according to claim 5, wherein a plurality of projections smaller than a gap between the main boss and the main detection electrode are provided on a surface of the main boss facing the main detection electrode. Capacitive micro flow sensor. 7. The sub-boss portion according to claim 5, wherein a plurality of projections smaller than a gap between the sub-boss portion and the sub-detection electrode are provided on a surface of the sub-boss portion facing the sub-detection electrode. Capacitive micro flow sensor. 8. A first substrate made of an insulating member and a second substrate made of a semiconductor member are joined to each other, and a conductive surface of the first substrate facing the second substrate is provided. A detection electrode formed of a conductive member, a boss portion facing the detection electrode via a predetermined gap is provided on a surface of the second substrate facing the first substrate; A measurement recess is formed around the bottom so that the bottom becomes a diaphragm, and a communication path communicating the measurement recess with the outside is formed. The communication passage is generated according to a pressure difference between the pressure in the measurement recess and the outside. A method for manufacturing a capacitance type micro flow sensor configured to be able to detect a change in capacitance of a capacitor formed by the detection electrode and the boss portion, the method comprising manufacturing the first substrate. (1) a substrate manufacturing process; A second substrate manufacturing step of manufacturing a board; and bonding the first substrate manufactured by the first substrate manufacturing step and the second substrate manufactured by the second substrate manufacturing step by anodic bonding The first substrate manufacturing process includes forming an oxide film on both surfaces of a silicon wafer formed in a predetermined shape and dimensions, applying a resist on the oxide film, and performing photolithography. After removing the resist in the portion to be the boss portion and the measurement concave portion, and further removing the oxide film in the portion where the resist has been removed, all the remaining registers are removed, and the remaining oxide film is used as a protective film Silicon etching is performed on the portion from which the oxide film has been removed for a predetermined time to remove silicon by a predetermined depth corresponding to a gap between the boss portion and a detection substrate provided on the first substrate. Step 1 and after the first step, an oxide film is formed again on both surfaces of the silicon wafer, a resist is applied on the oxide film, and the resist at a portion to be the measurement concave portion is removed by photolithography. Further, after removing the oxide film at the portion where the resist has been removed, all the remaining resist is removed, and the remaining oxide film is used as a protective film to perform silicon etching on the portion where the oxide film has been removed. And a second step of forming a measurement concave portion having a desired depth by applying a resist to one surface of a glass substrate, After removing the resist at the portion where the detection electrode is provided by photolithography, ITO is deposited on the entire surface of one of the surfaces, and then the ITO deposited on the resist is removed together with the resist. Method of manufacturing the capacitive micro-flow sensor characterized by comprising a step of forming the detection electrode was removed by-off. 9. An external fixation of a capacitance type macro flow sensor for externally attaching a capacitance type macro flow sensor for measuring a flow velocity of fuel in an injector used in a fuel injection device to the injector. A main fixing tool and a sub fixing tool, wherein the main fixing tool has a fuel passage formed in a hollow cylindrical shape, and one end of which is fitted with an end of the injector. The injector fitting hole to be fitted, the other end has a pipe fitting hole into which one end of a pipe connected to the fuel injection pump is fitted,
Each of the sub-fixtures is formed and formed with a sub-fixture fitting hole in which the sub-fixture is fitted in a direction orthogonal to the fuel passage. The sub-fixture is fitted into the sub-fixture fitting hole. Having a cylindrical fitting portion formed in a cylindrical shape,
A part of the semi-cylindrical portion is a detachably configured sensor fixing piece, and a part of the fuel passage is provided between the sensor fixing piece and the portion where the sensor fixing piece is attached. And a semi-cylindrical groove is formed, and a capacitance type micro flow sensor is sandwiched between the sensor fixing piece and a portion to which the sensor fixing piece is attached. An external fixture for an electrostatic capacitance type macro flow sensor, wherein the external fixture is provided.