JP2004283676A - Oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive oscillator which is used widely for a strain sensor, a vacuum sensor, a vibration sensor, a mechanical filter, an ultrasonic transducer, or the like, and can be miniaturized. <P>SOLUTION: This oscillator is provided with: a resistor arranged on the surface of this oscillator; an exciting means for exciting this oscillator by applying an electric current to the resistor; and a detecting means for detecting the vibration of this oscillator on the basis of the variation of the resistance value of the resistor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inexpensive vibrator that can be reduced in size.
Transducers have a wide range of applications such as strain sensors, vacuum sensors, vibration sensors, mechanical filters, and ultrasonic transducers.
[0002]
[Prior art]
FIG. 6 is an explanatory view of the configuration of a main part of a conventional example generally used in the related art. For example, it is shown in Japanese Utility Model Application Laid-Open No. 4-116748, entitled "Vibration type pressure measuring device" (for example, see Patent Reference 1).
7 is an enlarged explanatory view of a main part of FIG. 6, FIG. 8 is an enlarged explanatory view of a main part of FIG. 7, FIG. 9 is an explanatory view of the operation of FIG. 6, and FIG.
This is an example in which a vibration sensor is used in a pressure measuring device.
[0003]
In the figure, reference numeral 1 denotes a sensor chip made of a semiconductor single crystal.
Reference numeral 2 denotes a measurement diaphragm formed by the concave portion 3 provided in the sensor chip 1 and receiving the measurement pressure Pm.
[0004]
Reference numeral 4 denotes a strain detection sensor embedded in the measurement diaphragm 2 and uses a vibrator.
Reference numeral 5 denotes a shell made of a semiconductor epitaxial growth layer for sealing, and seals the vibrator 4 to the measurement diaphragm 2.
[0005]
Reference numeral 6 denotes a vacuum chamber provided around the vibrator 4, between the vibrator 4, the measurement diaphragm 2 and the shell 5.
[0006]
As shown in FIGS. 9 and 10, the vibrator 4 is configured to oscillate with the natural vibration of the vibrator 4 by the magnetic field of the permanent magnet 7 and the closed-loop self-excited oscillation circuit connected to the vibrator 4. I have.
The permanent magnet 7 is arranged to face the vibrator 4 via the yoke 8, the yoke holder 9, and the spacer 11.
In FIG. 10, the vibrator 4 has an H shape.
[0007]
The yoke holder 9 is loosely fitted on the bottom 22 side, the bottom 22 presses the yoke holder 9 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 Is a cap body having a U-shaped cross section and having elasticity, which is fixed to the support 12 by welding 25.
[0008]
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 sets the relative position between the vibrator 4 and the magnet 7 with high accuracy.
Reference numeral 26 denotes a hole provided at the center of the bottom 22.
[0009]
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 the change in the oscillation frequency.
[0010]
[Patent Document 1]
JP-A-4-116748 (pages 4-5, FIGS. 4, 6 and 7)
[0011]
[Problems to be solved by the invention]
However, in such an apparatus, a magnetic field is applied to the vibrator 4 for self-excited vibration of the vibrator 4.
The magnet 7 is required for the self-excited oscillation of the vibrator 4, which is one of the factors of high cost.
Further, since the magnet 7 is required, miniaturization becomes difficult.
[0012]
An object of the present invention is to solve the above-mentioned problems and to provide a vibrator which can be reduced in size and inexpensive.
[0013]
[Means for Solving the Problems]
In order to achieve such an object, in the present invention, in the vibrator according to claim 1,
A resistor provided on the surface of the vibrator, excitation means for applying a current to the resistor to excite the vibrator, and detecting means for detecting vibration of the vibrator from a change in the resistance value of the resistor It is characterized by having.
[0014]
According to a second aspect of the present invention, in the vibrator according to the first aspect,
The oscillator is manufactured by a micro-machining technique.
[0015]
According to a third aspect of the present invention, in the vibrator according to the first or second aspect,
The resistor is composed of an excitation resistor and a detection resistor.
[0016]
According to a fourth aspect of the present invention, in the vibrator according to any one of the first to third aspects,
A first insulating film provided between the vibrator and the resistor to insulate the vibrator and the resistor from each other.
[0017]
According to a fifth aspect of the present invention, in the vibrator according to any one of the first to fourth aspects,
A second insulating film is provided to cover the surface of the resistor and insulate the surface of the resistor.
[0018]
According to a sixth aspect of the present invention, in the vibrator according to any one of the first to fifth aspects,
A protection film provided over the surface of the second insulating film to protect the second insulating film;
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
1 is an explanatory view of a main part configuration of an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line bb of FIG. 1, FIG. 3 is a cross-sectional view taken along line aa of FIG. 1, and FIG. FIG. 5 and FIG. 5 are explanatory diagrams of the operation of FIG.
In the figure, the configuration of the same symbol as in FIG. 6 represents the same function.
Hereinafter, only differences from FIG. 6 will be described.
[0020]
The resistor 31 is provided on the surface of the vibrator 4.
In this case, the vibrator 4 is manufactured by a micromachining technique, is made of polysilicon, and employs fixed beams at both ends.
[0021]
In this case, the resistor 31 is made of polysilicon, and includes an excitation resistor 311 and a detection resistor 312.
Each of the resistors 311 and 312 has a folded-back resistor made of polysilicon on the surface of the root of the fixed-end vibrator 4.
[0022]
As shown in FIG. 4, the first insulating film 32 is provided between the vibrator 4 and the resistor 31, and insulates the vibrator 4 from the resistor 31.
In this case, it is made of a silicon oxide film.
[0023]
The second insulating film 33 is provided to cover the surface of the resistor 31 and insulates the surface of the resistor 31.
In this case, it is made of a silicon oxide film.
In this case, the second insulating film 33 and the first insulating film 32 are integrally formed.
[0024]
The protective film 34 is provided to cover the surface of the second insulating film 33 and protects the second insulating film 33.
In this case, it is made of polysilicon.
[0025]
As shown in FIG. 5, the excitation unit 41 applies a current to the resistor 311 to excite the vibrator 4.
The detecting means 42 detects the vibration of the vibrator 4 from the change in the resistance value of the resistor 312.
[0026]
In the above configuration, Joule heat is generated when a current flows through the folded resistor 311.
As the temperature rises, distortion occurs due to a difference in thermal expansion coefficient between the insulating film 32 and the vibrator 4 or a difference in temperature between the polysilicon resistor 311 and the vibrator 4.
[0027]
When a biased AC current flows through the polysilicon resistor 311, the amplitude increases when the current frequency matches the resonance frequency of the vibrator 4, so that excitation can be performed.
On the other hand, a direct current is passed through the folded resistor 312.
When the vibrator 4 resonates and the amplitude increases, the vibration can be detected by the piezoresistance effect.
[0028]
As a result,
(1) A magnet is not required, and an inexpensive vibrator can be obtained.
(2) Since there is no magnet, a vibrator that can be easily reduced in size can be obtained.
[0029]
(3) Since the vibrator 4 is manufactured by a micromachining technique, an extremely fine vibrator can be easily obtained.
[0030]
(4) Since the resistor 31 is composed of the excitation resistor 311 and the detection resistor 312, when excitation and vibration detection are performed by one resistor, the detected voltage is not sufficiently higher than the excitation voltage. And vibration cannot be detected.
[0031]
By independently forming the excitation resistor 311 and the detection resistor 312, it is possible to prevent the excitation voltage from being input to the detection circuit, and it is possible to detect only a signal due to resonance of the vibrator 4. become.
Therefore, a vibrator capable of detecting weaker vibration can be obtained.
[0032]
(5) Since the first insulating film 32 that is provided between the vibrator 4 and the resistor 31 and insulates the vibrator 4 from the resistor 31 is provided, the vibrator 4 is made of silicon or polysilicon. As described above, a vibrator capable of preventing a current flowing through the resistor 31 from leaking to the vibrator 4 when the vibrator has conductivity is obtained.
However, it is unnecessary when the vibrator 4 is made of an insulator such as glass or sapphire.
[0033]
(6) Since the second insulating film 33 provided to cover the surface of the resistor 31 and insulate the surface of the resistor 31 is provided, the resistor 31 is generally vibrated in the process of manufacturing the vibrator 4. In many cases, the vibrator 4 is formed by etching after being formed on the surface of the portion to be the vibrator 4.
[0034]
Depending on the etching means used and the resistor 31 or the material of the insulating film, the resistor 31 may be damaged in the step of etching the vibrator 4.
In this case, it is necessary to protect the resistor 31 or the insulating film with a protective film 34 by etching means. If the protective film 34 has conductivity, it is necessary to prevent a current flowing through the resistor 31 from leaking to the protective film 34. This is because an insulating film 33 is required between the resistor 31 and the protective film 34 in order to prevent this.
That is, a vibrator that can ensure the reliability in manufacturing can be obtained.
[0035]
(7) A protective film 34 is provided to cover the surface of the second insulating film 33 and protect the second insulating film 33.
In the process of manufacturing the vibrator 4, in many cases, the vibrator 4 is generally manufactured by etching after forming the resistor 31 on the surface of the portion to be the vibrator 4.
[0036]
Depending on the etching means used and the material of the resistor 31 or the insulating film, the resistor 31 may be damaged in the etching process of the vibrator 4.
In that case, it is necessary to protect the resistor 31 or the insulating film with a protective film 34 which is not attacked by the etching means.
That is, a vibrator that can ensure the reliability in manufacturing can be obtained.
[0037]
In the above-described embodiment, the vibrator 4 is described as being made of polysilicon. However, the present invention is not limited to this. For example, single crystal silicon, a silicon oxide film, a silicon nitride film, or the like may be used. In short, what is necessary is just to be excited and vibrate.
[0038]
Further, the vibrator 4 may be not only a beam fixed at both ends but also a diaphragm or a cantilever structure.
[0039]
In the above-described embodiment, the first insulating film 32 is described as a silicon oxide film. However, the present invention is not limited to this. For example, a silicon nitride film or non-doped polysilicon may be used. In short, any film having a high resistance may be used. However, when the vibrator 4 is an insulating film such as a silicon oxide film or a silicon nitride film, it is of course unnecessary.
[0040]
The second insulating film 33 is for insulating the polysilicon resistor, and uses, for example, a silicon oxide film.
However, it is not necessary depending on the configuration of the vibrator 4 and the situation in which it is used, for example, depending on the process used.
[0041]
The protection film 34 is for protecting the insulating film 32 between the polysilicon resistor 21 and the vibrator 4 when the vibrator 4 is manufactured by, for example, etching a sacrificial layer oxide film using hydrofluoric acid. , Polysilicon is used.
However, it is not necessary depending on the configuration of the vibrator 4 and the situation in which it is used, for example, depending on the process used.
[0042]
It should be noted that the foregoing description has been directed to specific preferred embodiments for the purpose of explanation and illustration of the present invention. Therefore, the present invention is not limited to the above-described embodiment, but includes many more changes and modifications without departing from the spirit thereof.
[0043]
【The invention's effect】
As described above, according to the first aspect of the present invention, the following effects can be obtained.
(1) A magnet is not required, and an inexpensive vibrator can be obtained.
(2) Since there is no magnet, a vibrator that can be easily reduced in size can be obtained.
[0044]
According to the second aspect of the present invention, the following effects are obtained.
Since the vibrator is manufactured by a micromachining technique, an extremely fine vibrator can be easily obtained.
[0045]
According to the third aspect of the present invention, the following effects are obtained.
Since the resistor is composed of a resistor for excitation and a resistor for detection, if excitation and vibration detection are performed with one resistor, vibration cannot be detected unless the detection voltage is sufficiently higher than the excitation voltage. .
By independently forming the excitation resistor and the detection resistor, it is possible to prevent the excitation voltage from being input to the detection circuit, and it is possible to detect only a signal due to resonance of the vibrator.
Therefore, a vibrator capable of detecting weaker vibration can be obtained.
[0046]
According to claim 4 of the present invention, the following effects are obtained.
Since the first insulating film provided between the vibrator and the resistor and insulating the vibrator and the resistor is provided, when the vibrator has conductivity such as silicon or polysilicon, A vibrator capable of preventing a current flowing through the resistor from leaking to the vibrator is obtained.
However, it is unnecessary when the vibrator is made of an insulator such as glass or sapphire.
[0047]
According to claim 5 of the present invention, the following effects are obtained.
Since the second insulating film is provided to cover the surface of the resistor and insulate the surface of the resistor, the resistor is generally formed on the surface of the portion to be the oscillator in the process of manufacturing the oscillator. After that, the vibrator is often manufactured by etching.
[0048]
Depending on the etching means used and the resistor or the material of the insulating film, the resistor may be damaged in the step of etching the vibrator.
In that case, it is necessary to protect the resistor or the insulating film with a protective film by etching means, but when the protective film has conductivity, in order to prevent a current flowing through the resistor from leaking to the protective film, This is because an insulating film is required between the resistor and the protective film.
That is, a vibrator that can ensure the reliability in manufacturing can be obtained.
[0049]
According to claim 6 of the present invention, the following effects are obtained.
A protective film provided to cover the surface of the second insulating film and to protect the second insulating film was provided.
In a process of manufacturing a vibrator, generally, a vibrator is often manufactured by etching after forming a resistor on a surface of a portion to be a vibrator.
[0050]
Depending on the etching means used and the resistor or the material of the insulating film, the resistor may be damaged in the step of etching the vibrator.
In that case, it is necessary to protect the resistor or the insulating film with a protective film that is not affected by the etching means.
That is, a vibrator that can ensure the reliability in manufacturing can be obtained.
[0051]
Therefore, according to the present invention, a vibrator which can be reduced in size and inexpensive can be realized.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a main configuration of an embodiment of the present invention.
FIG. 2 is a sectional view taken along line bb of FIG. 1;
FIG. 3 is a sectional view taken along line aa of FIG. 1;
FIG. 4 is an enlarged explanatory view of a main part of FIG. 1;
FIG. 5 is an operation explanatory diagram of FIG. 1;
FIG. 6 is an explanatory diagram of a configuration of a main part of a conventional example generally used in the related art.
FIG. 7 is an enlarged explanatory view of a main part of FIG. 6;
FIG. 8 is an enlarged explanatory view of a main part of FIG. 7;
FIG. 9 is an operation explanatory diagram of FIG. 6;
FIG. 10 is an operation explanatory diagram of FIG. 6;
[Explanation of symbols]
REFERENCE SIGNS LIST 1 sensor chip 2 measurement diaphragm 3 recess 4 oscillator 5 shell 6 vacuum chamber 7 permanent magnet 8 yoke 9 yoke holder 11 spacer 12 support 21 cap body 22 bottom 23 opening 24 opening edge 25 welding 26 hole 31 resistor 311 resistor 312 Resistor 32 First insulating film 33 Second insulating film 34 Protective film 41 Exciting means 42 Detecting means

Claims (6)

A resistor provided on the surface of the vibrator;
Excitation means for applying a current to the resistor to excite the vibrator;
A vibrator comprising: a detection unit configured to detect vibration of the vibrator from a change in a resistance value of the resistor. The vibrator according to claim 1, wherein the vibrator is manufactured by a micromachining technique. The vibrator according to claim 1, wherein the resistor includes an excitation resistor and a detection resistor. 4. The device according to claim 1, further comprising a first insulating film provided between the vibrator and the resistor to insulate the vibrator and the resistor. 5. Vibrator. The vibrator according to claim 1, further comprising a second insulating film provided to cover a surface of the resistor and insulating the surface of the resistor. The vibrator according to claim 1, further comprising a protective film provided to cover a surface of the second insulating film and to protect the second insulating film.

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