JP2005140614A - Oscillating type pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an oscillating type pressure sensor which has an improvement in S/N ratio. <P>SOLUTION: The oscillating type pressure sensor includes a measuring diaphragm to which a measuring pressure is applied, and an oscillating beam provided in this measuring diaphragm. The oscillating type pressure sensor further includes an oscillating beam body having an I-shape insulator provided in the measuring diaphragm, a drive oscillating beam provided on the one side surface side of the oscillating beam body and made of a conductor, and a detecting oscillating beam provided on the other side surface side of this oscillating beam body and made of a conductor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vibration type pressure sensor having an improved S / N ratio.

Prior art documents related to the vibration type pressure sensor include the following.
JP-A-4-116748 (page 4-5, FIG. 4, FIG. 6, FIG. 7)

FIG. 10 is an explanatory diagram showing the structure of a main part of a conventional example that is generally used in the past. For example, it is shown in Japanese Utility Model Publication No. 4-116748 and the name of the device “vibration type pressure measuring device”.
FIG. 11 is an enlarged detailed view of the main part of FIG. 10, FIG. 12 is an enlarged explanatory view of the main part of FIG. 11, FIG. 13 is an operational explanatory view of FIG. 10, and FIG.
This is an example in which a vibration sensor is used in a pressure measuring device.

In the figure, reference numeral 1 denotes a sensor chip made of a semiconductor single crystal.
Reference numeral 2 denotes a measurement diaphragm that is formed by the recess 3 provided in the sensor chip 1 and receives the measurement pressure Pm.

Reference numeral 4 denotes a strain detection sensor embedded in the measurement diaphragm 2, which uses a vibrator.
Reference numeral 5 denotes a shell made of a semiconductor epitaxial growth layer for sealing, which seals the vibrator 4 to the measurement diaphragm 2.

  Reference numeral 6 denotes a vacuum chamber provided around the vibrator 4 and between the vibrator 4, the measurement diaphragm 2 and the shell 5.

As shown in FIGS. 13 and 14, the vibrator 4 is configured to oscillate with the natural vibration of the vibrator 4 by a magnetic field generated by the permanent magnet 7 and a closed-loop self-excited oscillation circuit connected to the vibrator 4. Yes.
The permanent magnet 7 is disposed to face the vibrator 4 via the yoke 8, the yoke holder 9, and the spacer 11.
In FIG. 14, the vibrator 4 has an H shape.

  21, the yoke holder 9 is loosely fitted on the bottom 22 side, the bottom 22 is pressed against the spacer 11 in the direction of the vibrator 4, the support 12 is loosely fitted on the opening 23 side, and the opening edge 24 2 is a cap body having a U-shaped cross section and having elasticity that is fixed to the support 12 by welding 25.

The cap body 21 is made of a material having a thermal expansion coefficient close to that of the yoke holder 9 and the support body 12, and accurately sets the relative position between the vibrator 4 and the magnet 7.
A hole 26 is provided at the center of the bottom 22.

In the above configuration, when the measurement pressure Pm is applied to the measurement diaphragm 2, the axial force of the vibrator 4 changes and the natural frequency changes, so that the measurement pressure Pm can be measured by changing the oscillation frequency.
In this case, the drive current i0 is supplied to the excitation side of the vibrator 4 to excite the H-type vibrator 4, and the resonance frequency is detected by the induced electromotive force eout generated on the detection side.
Here, as shown in FIG. 14, R 1 is the resistance of the vibrator 4, and R 2 is the resistance of the shell 5.

However, in such a device,
(1) The output voltage eout is small due to limitations on the vibrator shape and magnetic flux density.
(2) Since the vibrator and the shell portion are not electrically insulated, the drive current i0 leaks to the shell side.
(3) Since the excitation side and the detection side of the vibrator are not electrically insulated, the drive current i0 leaks to the detection side and increases the crosstalk level.

Due to the above (1) to (3), the S / N ratio of the output voltage of the vibrator 4 is deteriorated.
In addition, due to the mode crossing in the harmonic resonance mode unique to the H-type structure, there is a design restriction as a differential pressure / pressure sensor (differential pressure sensitivity cannot be increased, normal operating conditions: static pressure cannot be increased). there were.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and an object thereof is to provide a vibration sensor having a high sensitivity and a large dynamic range that has an excellent S / N ratio and eliminates restrictions on use.

In order to achieve such a subject, in the present invention, in the vibration type pressure sensor of claim 1,
In a vibration type pressure sensor comprising: a measurement diaphragm to which a measurement pressure is applied; and a vibrating beam provided on the measurement diaphragm.
A vibrating beam main body made of an I-shaped insulating material provided on the measurement diaphragm, a driving vibrating beam portion made of a conductor provided on one side of the vibrating beam main body, and provided on the other side of the vibrating beam main body. And a detection vibration beam portion made of a conductor.

According to claim 2 of the present invention, in the vibration type pressure sensor according to claim 1,
The vibrating beam body is made of a silicon material.

In Claim 3 of this invention, in the vibration type pressure sensor of Claim 1 or Claim 2,
The drive vibration beam portion is formed by injecting boron or phosphorus into the vibration beam main body.

According to a fourth aspect of the present invention, in the vibration type pressure sensor according to the first or second aspect,
The detection vibration beam portion is formed by injecting boron or phosphorus into the vibration beam main body.

According to Claim 5 of the present invention, in the vibration type pressure sensor according to any one of Claims 1 to 4,
The vibrating beam main body is provided on the measurement diaphragm via an insulating film.

According to a sixth aspect of the present invention, in the vibration type pressure sensor according to the fifth aspect,
The insulating film is a silicon oxide film.

According to the first to fourth aspects of the present invention, the following effects can be obtained.
(1) Since the excitation side and the detection side are electrically insulated, a vibration type pressure sensor with a reduced crosstalk level can be obtained.
(2) By adopting the I-type simple structure, it is possible to obtain a vibration type pressure sensor that does not cause mode crossing due to harmonic resonance, which is a limitation of the H-type design.
For the above reasons, a vibration sensor having an excellent S / N ratio can be obtained.

According to claims 5 and 6 of the present invention, the following effects can be obtained.
Since the vibrator and the shell are insulated by the insulating film, a vibration type pressure sensor in which the drive current does not flow in the shell can be obtained.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention, and FIGS. 2 to 9 are manufacturing explanatory diagrams of FIG.
In the figure, the vibrating beam main body 31 is made of an I-shaped insulating material provided on the measurement diaphragm 2 via an insulating film 32 (not shown).

The drive vibration beam portion 33 is provided on one side of the vibration beam main body 31 and is made of a conductor.
The detection vibration beam portion 34 is provided on the other side of the vibration beam main body 31 and is made of a conductor.
In this case, the vibrating beam body 31 is made of a silicon material. In this case, the drive vibrating beam portion 33 is formed by injecting boron or phosphorus into the vibrating beam body 31.

In this case, the detection vibration beam portion 34 is formed by injecting boron or phosphorus into the vibration beam main body 31.
Reference numeral 41 denotes a lead portion, which is provided at four locations.
Reference numeral 42 denotes an electrode connected to the lead portion.

(1) Since the drive vibration beam portion 33 and the detection vibration beam portion 34 of the I-type vibrator are electrically insulated by the PN junction, the drive current i0 is leaked to the detection side and the crosstalk level is increased. A vibration type sensor that can be prevented from being generated is obtained.
(2) The structure can be simplified with type I, and an inexpensive vibration sensor can be obtained.
(3) The drive current flowing in the shell can be significantly reduced by sandwiching an insulating film (SiO2) between the vibrator and the shell.

In the above configuration, when the measurement pressure Pm is applied to the measurement diaphragm 2, the axial force of the vibrating beams 33 and 34 changes, and the natural frequency changes, so that the measurement pressure Pm can be measured by the change of the oscillation frequency.
In this case, the drive current i0 is supplied to the excitation side of the vibration 33 to excite the vibrating beam 34, and the resonance frequency is detected by the induced electromotive force eoutpp generated on the detection side.

Such a vibrator is manufactured as shown in FIGS.
As shown in FIG. 2, an SOI substrate is used.
As shown in FIG. 3, boron or phosphorus is implanted into the corresponding portions of the drive vibration beam portion 33, the detection vibration beam portion 34, and the lead portion 41 of the SOI layer 101.

As shown in FIG. 4, the SOI layer 101 is dry-etched to form a vibrator portion.
As shown in FIG. 5, the silicon oxide layer 104 is formed on the silicon oxide layer 102, the driving vibration beam portion 33, the detection vibration beam portion 34, and the lead portion 41 by a CVD method (chemical vapor deposition method).

As shown in FIG. 6, a polysilicon layer 105 is formed on the silicon oxide layer 10 4 by CVD (chemical vapor deposition).
As shown in FIG. 7, a fine hole 106 for etching the silicon oxide layers 102 and 104 is formed in the polysilicon layer 105 by dry etching.

At the same time, the polysilicon layer 105 where the electrode 14 is formed is also etched.
As shown in FIG. 8, the silicon oxide layers 102 and 104 are wet-etched through the narrow holes 106.
As shown in FIG. 9, a polysilicon layer 106 is stacked on the polysilicon layer 105 and sealed.

  In the above-described embodiment, it has been described that the wafer on which the vibration sensor is formed is made of SOI. However, the present invention is not limited to this, and may be, for example, SIOX.

  The above description merely shows a specific preferred embodiment for the purpose of explanation and illustration of the present invention. Therefore, the present invention is not limited to the above-described embodiments, and includes many changes and modifications without departing from the essence thereof.

As a result,
The present invention has the following effects.
(1) Since the excitation side 33 and the detection side 34 are electrically insulated, a vibration type pressure sensor with a reduced crosstalk level can be obtained.

(2) By adopting the simple structure of the I-type 31, a vibration type pressure sensor can be obtained in which mode crossing due to harmonic resonance, which is a limitation of the H-type design, does not occur.
(3) Since the vibrator and the shell are insulated by the insulating film 32, a vibration type pressure sensor in which the drive current does not flow in the shell is obtained. For the reasons (1) to (3) above, the S / N ratio is An excellent vibration sensor can be obtained.

It is principal part structure explanatory drawing of one Example of this invention. It is manufacture explanatory drawing of FIG. It is manufacture explanatory drawing of FIG. It is manufacture explanatory drawing of FIG. It is manufacture explanatory drawing of FIG. It is manufacture explanatory drawing of FIG. It is manufacture explanatory drawing of FIG. It is manufacture explanatory drawing of FIG. It is manufacture explanatory drawing of FIG. It is principal part structure explanatory drawing which shows an example of the conventional vibration type pressure sensor. It is principal part expansion explanatory drawing of FIG. It is a principal part expansion explanatory drawing of FIG. It is operation | movement explanatory drawing of FIG. It is operation | movement explanatory drawing of FIG. It is operation | movement explanatory drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor chip 2 Measurement diaphragm 3 Recessed part 4 Strain detection sensor 5 Shell 6 Vacuum chamber 7 Permanent magnet 8 Yoke 9 Yoke holder 11 Spacer 21 Cap body 22 Bottom part 23 Opening part 24 Opening edge part 25 Welding 26 Hole 31 Vibrating beam main body 32 Insulating film 33 Drive vibration beam portion 34 Detected vibration beam portion 41 Lead portion 42 Electrode eout Induced electromotive force i0 Drive current R1 Oscillator resistance R2 Shell resistance

Claims (6)

In a vibration type pressure sensor comprising a measurement diaphragm to which a measurement pressure is applied and a vibrating beam provided on the measurement diaphragm,
A vibrating beam main body made of an I-shaped insulating material provided on the measurement diaphragm;
A drive vibration beam portion made of a conductor provided on one side of the vibration beam body;
A vibration type pressure sensor comprising: a detection vibration beam portion made of a conductor provided on the other side surface of the vibration beam main body. The vibration type pressure sensor according to claim 1, wherein the vibration beam main body is made of a silicon material. The vibration type pressure sensor according to claim 1 or 2, wherein the drive vibration beam portion is formed by injecting boron or phosphorus into the vibration beam main body. The vibration type pressure sensor according to claim 1, wherein the detection vibration beam portion is formed by injecting boron or phosphorus into the vibration beam main body. The vibration type pressure sensor according to any one of claims 1 to 4, wherein the vibration beam main body is provided on the measurement diaphragm via an insulating film. The vibration type pressure sensor according to claim 5, wherein the insulating film is a silicon oxide film.

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