JP4512864B2 - Gas rate sensor - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a gas type rate sensor that electrically detects a deflection state of a gas flow according to an angular velocity acting on a sensor body.
[0002]
[Prior art]
In general, in a gas type rate sensor, gas is jetted from a nozzle hole in a sensor body toward a heat sensor composed of thermal resistance elements provided on the left and right sides of the gas passage by a pump, and the sensor body is externally provided. When the gas flow flowing in the gas passage is deflected in the left-right direction due to the addition of the angular velocity motion, the electric signal corresponding to the change state of the resistance value generated in the heat sensor is taken out, and then it acts on the sensor body. The direction and magnitude of the angular velocity is detected.
[0003]
As this kind of gas type rate sensor, a sensor body consisting of a nozzle hole, a gas passage and a heat sensor provided in the gas passage has been developed as an ultra-small one formed by micromachining by etching a semiconductor substrate. (For example, refer to Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-2027
As shown in FIGS. 8 to 10, the sensor body in the gas type rate sensor is such that a small groove 15 for a nozzle hole, a half groove 16 for a gas passage, and a sensor bridge 17 for the gas passage etch a semiconductor substrate. A gas supply port 19 connected to the lower groove 14 for gas passage and a small groove 15 for nozzle holes on the upper surface, and a gas discharge port 20 to the rear of the gas groove half groove 18. The nozzle holes 25 and the gas passages 26 are formed by superimposing the upper substrates 21 formed thereon and bonding them together.
[0006]
On the upper surface of the sensor bridge 17, heat sensors 22 and 23 made of a heat-sensitive resistance material such as a pair of left and right platinum are formed in a pattern. In the figure, reference numeral 24 denotes each electrode of the heat sensors 22 and 23.
[0007]
Then, as shown in FIG. 11, gas is fed from the gas supply port 19 of the sensor body 28 using a piezoelectric pump 27 separately manufactured by metal processing, and the gas flow from the nozzle hole 25 into the gas passage 26. It is trying to produce.
[0008]
Therefore, when the sensor body 28 is fine by micromachining, the gas flow ejected from the nozzle hole 25 into the gas passage 26 by the pump 27 leads to the detection accuracy of the angular velocity in the sensor body 28.
[0009]
At that time, the pump 27 is assembled to the sensor body 28 so that the gas supply port 19 of the sensor body 28 and the discharge port of the pump 27 are directly connected. It becomes difficult to maintain the joining accuracy between the two, such as misalignment, and if the joining position between the two is misaligned, the sensor main body 28 is disturbed in gas flow.
[0010]
Therefore, conventionally, as shown in FIG. 11, the sensor main body 28 and the pump 27 are respectively fixed to a stay (not shown), and a nozzle 29 is attached to the gas supply port 19 of the sensor main body 28 so that the pump The discharge ports 22 and the nozzles 29 are connected by a tube 30.
[0011]
However, if such a connecting means for the sensor main body 28 and the pump 27 is used, the number of parts increases and the assembling workability deteriorates, and the entire apparatus becomes large. In addition, the displacement of the joining position between the sensor main body 28 and the pump 27 cannot be completely eliminated.
[0012]
In addition, although not disclosed, as shown in FIG. 12, the applicant integrally has a pump 32 manufactured by micromachining of the semiconductor substrate integrally formed on the sensor body 31 manufactured by micromachining of the semiconductor substrate. A gas type rate sensor was previously proposed which was designed to reduce the size and improve the bondability (see, for example, Patent Document 2).
[0013]
[Patent Document 2]
Japanese Patent Application No. 2002-383097 [0014]
It is oscillated by a piezoelectric element 33 bonded to the upper surface of the sensor main body 31 and bonded to the upper surface, and a vibration plate 35 having a vent hole 34 formed on one side is formed. The pump is constituted by a first substrate 38 forming a pump intake / exhaust chamber 37 provided with 36, and a second substrate 40 formed on and bonded to the first substrate 38 to form a pump back pressure chamber 39. I am trying to configure it.
[0015]
However, even in the gas type rate sensor configured as described above, if the center position of the vent hole 34 and the gas supply port 19 is relatively displaced during assembly, the back pressure chamber 39 passes through the vent hole 34. The gas discharged toward the gas supply port 19 may be disturbed or the flow rate may be reduced.
[0016]
[Problems to be solved by the invention]
The problem to be solved is that when assembling a pump manufactured by metal processing separately to a sensor body manufactured by micromachining processing of a semiconductor substrate, it is difficult to maintain the coupling accuracy by directly connecting the two. If a connecting member such as a joint tupe is used, the assembling workability is deteriorated and the entire apparatus is enlarged.
[0017]
Also, in order to reduce the size and improve the bondability between the sensor body and the pump, the pump manufactured by micromachining the semiconductor substrate is integrated with the sensor body manufactured by micromachining the semiconductor substrate. Assembling to the sensor body causes a problem that the gas supplied to the sensor body is disturbed or the flow rate is lowered if the relative assembly accuracy between the sensor body and the pump is poor.
[0018]
[Means for Solving the Problems]
In the gas type rate sensor according to the present invention, the sensor main body and the pump are integrally manufactured by micromachining processing of a semiconductor substrate, so that the coupling accuracy between the two is maintained and a stable gas flow is always supplied to the sensor main body. So that it can be generated.
[0019]
Specifically, a vibration plate that is vibrated by an electromagnetic vibrator is formed between the lower substrate and the upper substrate, an exhaust hole is formed in a base portion that supports the vibration plate, and a heat wire sensor bridge is formed. The formed intermediate substrate is sandwiched between the lower substrate and the upper substrate, and an intake port of the pump unit is formed at one side end portion between the upper substrate and the intermediate substrate, and communicated with the intake port. An intake / exhaust chamber is formed , a vent hole is formed between the intermediate substrate and the lower substrate on the exhaust hole side, and the lower side so as to communicate with the vent hole in the direction along the substrate via the vent hole A back pressure chamber of the pump unit and a nozzle hole for gas supply of the sensor unit are formed between the substrate and the intermediate substrate. The sensor unit communicates with the nozzle hole between the upper substrate and the lower substrate. A gas passage is formed and communicates with the gas passage to connect the upper substrate and the intermediate substrate. In said intake port is configured so that the gas outlet of the sensor portion to the other side edge portion is formed.
[0020]
【Example】
In the gas type rate sensor according to the present invention, as shown in FIG. 1, a vibration plate 31 that is vibrated by the piezoelectric element 4 is formed between the lower substrate 1 and the upper substrate 2. An intermediate substrate 3 having an exhaust hole 5 formed in the supporting base 32 and a heat-bridge sensor bridge 6 is sandwiched between the upper substrate 2 and the intermediate substrate 3, and the intake port 7 and the suction port of the pump unit B are interposed between the upper substrate 2 and the intermediate substrate 3. An exhaust chamber 8 and a gas discharge port 9 of the sensor unit A are formed, and gas is supplied to the back pressure chamber 10 of the pump unit B, the vent hole 11 and the sensor unit A between the lower substrate 1 and the intermediate substrate 3. The nozzle hole 12 is formed, and the gas passage 13 of the sensor unit A is formed between the lower substrate 1 and the upper substrate 2.
[0021]
The nozzle hole 12 for gas supply of the sensor unit A also serves as a gas discharge port of the pump unit B, and a vent hole 11 is provided on the side of the exhaust hole 5 formed in the intermediate substrate 3. A nozzle hole 12 is provided so as to communicate with the direction along the substrate.
[0022]
The upper substrate 2 is formed with a recess serving as the intake / exhaust chamber 8, a notch serving as the air inlet 7, and a recess serving as the upper portion of the gas passage 13 by etching the semiconductor substrate.
[0023]
The intermediate substrate 3 is formed with a recess that becomes the diaphragm 31 and the back pressure chamber 10, an exhaust hole 5, a sensor bridge 6, and a notch portion that becomes a gas exhaust port 9 by etching the semiconductor substrate. A part of the base 32 that supports the vibration plate 31 is cut away to form a vent hole 11 and a nozzle hole 12 connected to the back pressure chamber 10 with the lower substrate 1.
[0024]
At that time, a vent hole 11 is provided on the side of the exhaust hole 5 formed in the intermediate substrate 3, and a nozzle hole 12 is provided so as to communicate with the vent hole 11 in a direction along the substrate.
[0025]
The sensor bridge 6 provided with the heat sensor is installed at a position slightly higher than the nozzle hole 12 in consideration of the gas flow popping up due to heat.
[0026]
FIG. 2 shows a chip cut-out state from a silicon wafer for obtaining semiconductor substrates used for the lower substrate 1, the upper substrate 2 and the intermediate substrate 3.
[0027]
Note that the lower substrate 1 may not be a dedicated semiconductor substrate, but may be various other substrates on which a micropump is mounted.
[0028]
Here, the vibration plate 31 is vibrated using the piezoelectric element 4, but instead of using the piezoelectric element 4, other electromagnetically vibrating electrostrictive vibrators, magnetostrictive vibrators and the like are widely used. Nor.
[0029]
Further, in the present invention, when the diaphragm 31 is formed on the intermediate substrate 3, as shown in FIGS. 3 and 4, one side consisting of the (100) plane of the silicon wafer is anisotropically etched to reduce the thickness. The formed diaphragm 31 is formed.
[0030]
Micromachining processing of a silicon wafer includes processing techniques using dry etching and wet etching. Each etching has an isotropic etching that etches in all directions and an anisotropic etching that selectively etches in a specific direction, and is different in the photolithographic technology that three-dimensionally processes a silicon wafer. Relatively many etchings are used.
[0031]
In the present invention, the etching rate is fast, the throughput is good, the cost can be reduced by batch processing, and the wet etching, which is more productive than the dry etching, is adopted to anisotropically etch the silicon wafer. I have to. At this time, when the (100) plane of the silicon wafer is etched, the diaphragm 31 is processed into a quadrangular pyramid shape having a side surface composed of the (111) plane to form a square-shaped diaphragm 31.
[0032]
The etched portion is in a state in which the plane formed by the (100) plane and the side surface formed by the (111) plane are exposed. The (111) plane is a stable crystal plane that finally appears in anisotropic wet etching, and the entire circumference of the diaphragm 31 formed into a thin film by etching is supported by the portion made of the (111) plane. Thus, it is possible to easily obtain the diaphragm 31 that is stable and structurally strong and can always exhibit constant vibration characteristics without variation.
[0033]
On the square diaphragm 31, as shown in FIG. 5, the stress applied to the diaphragm 31 by the piezoelectric element 4 during vibration is evenly distributed on the circumference and partially concentrated. The circular flat piezoelectric element 4 is bonded with the same center so as not to be present.
[0034]
The operation of the micropump according to the present invention configured as described above will be described below.
[0035]
First, as shown in FIG. 6, when a positive drive voltage is applied to the piezoelectric element 4 and the diaphragm 31 bends upward, the intake / exhaust chamber 8 becomes positive pressure and the back pressure chamber 10 becomes negative pressure. The gas in the intake / exhaust chamber 8 is sent into the back pressure chamber 10 through the exhaust hole 5 and the vent hole 11. In the figure, the arrows indicate the gas flow at that time.
[0036]
Next, as shown in FIG. 7, when a negative drive voltage is applied to the piezoelectric element 4 and the diaphragm 31 bends downward, the back pressure chamber 10 becomes positive pressure, and the gas in the back pressure chamber 10 Is discharged to the nozzle hole 12 through the vent hole 11. At the same time, the intake / exhaust chamber 8 becomes negative pressure, and gas is sucked into the intake / exhaust chamber 8 from the intake port 7. In the figure, the arrows indicate the gas flow at that time.
[0037]
By repeating such a pump operation, gas is intermittently ejected from the nozzle hole 12 into the gas passage 13, and a gas flow (laminar flow) is generated in the gas passage 13.
[0038]
At that time, in particular, according to the present invention, the nozzle hole 12 is provided so as to communicate with the vent hole 11 in the direction along the substrate, and the gas in the back pressure chamber 10 is discharged straight in the lateral direction. Therefore, the gas can be efficiently and stably discharged from the nozzle hole 12 into the gas passage 13 without causing a turbulent flow or reducing the flow rate.
[0039]
【The invention's effect】
As described above, according to the present invention, by integrally manufacturing the sensor body and the pump by micromachining a semiconductor substrate, the overall structure can be simplified and the miniaturization can be sufficiently achieved. The accuracy is maintained, and the pump performance and the sensor performance are excellent.
[0040]
At that time, in particular, according to the present invention, the intermediate substrate on which the diaphragm is formed by etching the semiconductor substrate is sandwiched between the upper substrate and the lower substrate at the base portion supporting the diaphragm. The mounting state of the diaphragm is always constant, and the pump performance with no variation in the vibration characteristics can be exhibited.
[0041]
And, since the gas in the back pressure chamber is discharged straight into the gas passage of the sensor body through the nozzle hole 12 in the lateral direction along the substrate, the turbulent flow is caused or the flow rate is reduced. In addition, there is an advantage that the gas can be efficiently supplied into the gas passage and the gas flow can be generated with a good laminar flow.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing a configuration example of a gas type rate sensor according to the present invention.
FIG. 2 is a diagram showing a chip cut-out state from a silicon wafer for obtaining a semiconductor substrate used for a lower substrate, an upper substrate, and an intermediate substrate in the same example.
FIG. 3 is a front sectional view showing an intermediate substrate on which a diaphragm is formed by etching a semiconductor wafer. FIG. 4 is a perspective view of the intermediate substrate on which the diaphragm is formed.
FIG. 5 is a plan view showing a state in which a circular electrostrictive vibrator is mounted on a rectangular diaphragm in the same embodiment.
FIG. 6 is a front sectional view showing one operating state of a micropump according to an embodiment of the present invention.
FIG. 7 is a front sectional view showing another operation state of the micropump according to the embodiment of the present invention.
FIG. 8 is a plan view showing a lower semiconductor substrate of a sensor main body in a general gas type rate sensor.
FIG. 9 is a back view showing an upper semiconductor substrate of a sensor main body in the general gas type rate sensor.
FIG. 10 is a side sectional view of a nozzle hole portion of a sensor main body in the general gas type rate sensor.
FIG. 11 is a perspective view showing an example of a connection state between a conventional sensor body and a pump.
FIG. 12 is a front sectional view of a gas type rate sensor in which a conventional micromachined sensor body and a pump are integrally assembled.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Lower substrate 2 Upper substrate 3 Intermediate substrate 31 Diaphragm 4 Piezoelectric element 5 Exhaust hole 6 Sensor bridge 7 Intake port 8 Intake / exhaust chamber 9 Gas exhaust port 10 Back pressure chamber 11 Vent hole 12 Nozzle hole 13 Gas passage

Claims (2)

An intermediate substrate in which a diaphragm that is vibrated by an electromagnetic vibrator is formed between the lower substrate and the upper substrate, an exhaust hole is formed in a base that supports the diaphragm, and a sensor bridge of a heat wire is formed Is sandwiched between the lower substrate and the upper substrate, and an intake port of the pump unit is formed at one side end between the upper substrate and the intermediate substrate, and an intake / exhaust chamber is formed in communication with the intake port A vent hole is formed between the intermediate substrate and the lower substrate on the exhaust hole side, and the lower substrate and the intermediate substrate are connected to the vent hole in a direction along the substrate through the vent hole. A back pressure chamber of the pump unit and a nozzle hole for gas supply of the sensor unit are formed between them, and a gas passage of the sensor unit is formed between the upper substrate and the lower substrate in communication with the nozzle hole. , Communicating with the gas passage, the intake air between the upper substrate and the intermediate substrate Configured Gas rate sensor such that the gas outlet of the sensor portion to the other side edge portion is formed with. The intermediate substrate is made of a semiconductor substrate formed with a recess that becomes a diaphragm and a back pressure chamber by etching, an exhaust hole, a sensor bridge, and a cutout portion that becomes a gas discharge port, and the upper substrate is a recess that becomes an intake and exhaust chamber by etching, It consists semiconductor substrate recess to be cut portion and a gas passage upper comprising an intake port is formed, gas rate according of claims 1 to lower substrate is characterized in that it is a mounting substrate gas rate sensor Sensor .

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