JP2513280B2 - Mechanical filter - Google Patents

Description

The present invention relates to a mechanical filter using a vibrating beam formed on a silicon substrate.

<Prior Art> FIGS. 5 to 7 are explanatory views of a configuration of a conventional example which is generally used from the prior art.

FIG. 5 is an explanatory view of the basic configuration, and FIG. 6 is AA of FIG.
Sectional views, FIGS. 7 (A) and 7 (B), are diagrams showing an electric circuit in FIG. 5, and FIG. 7 (B) shows a case where a reverse bias voltage is applied between the p-type layer and the n ^{+ -type} layer. Shows the power supply for doing.

In these figures, 11 is a p-type silicon substrate having a (100) plane, for example, an impurity concentration of 10 ¹⁵ atoms / cm ³ or less.

An n ⁺ diffusion layer (not shown) having an impurity concentration of about 10 ¹⁷ is partially formed on the surface of the substrate 11, and a vibrating beam 12 is formed in the <001> direction on a part of the n ⁺ diffusion layer. ing. The vibrating beam 12 is formed by processing the n ⁺ layer and the p layer formed on the substrate 11 by using photolithography and under etching techniques.

Reference numeral 13 is a magnet provided in the upper part of the center of the vibrating beam 12 orthogonally to the vibrating beam 12 and in a non-contact state, and 14 is a SiO ₂ film (see FIG. 6) as an insulating film.

15a and 15b are metal electrodes such as aluminum (Al), and one end of the metal electrode 15a is n ⁺ extending from the vibrating beam 12.
Layer is connected through a contact hole 16a provided in the SiO ₂ layer, and the other end is connected through a lead wire to one end of the amplifier 20 and the comparison resistor R _{0 which} is approximately equal to the resistance value of the vibrating beam 12.

The output of the amplifier 20 is taken out as an output signal and is branched and connected to one end of the primary coil L ₁ . The other end of this coil L ₁ is connected to the common line.

On the other hand, the other end of the comparison resistor R ₀ is connected to the other end of the secondary coil L ₂ whose middle point is connected to the common line, and the other end of the secondary coil L ₂ is formed on the other end of the vibrating beam 12 in the same manner as above. Metal electrode
It is connected to 15b.

In the above structure, a reverse bias voltage is applied between the p-type layer (substrate 10) and the n ^{+ -type} layer (vibrating beam 12) to insulate the vibrating beam.
When an alternating current i is applied to 12, the impedance of the vibrating beam increases due to the electromagnetic induction effect at the resonance frequency of the vibrating beam 12, and the comparative resistance R ₀ and the midpoint are connected to the common line.
An unbalanced signal can be obtained by the bridge formed by L ₂ . This signal is amplified by the amplifier 20 and taken out as an output signal.

In the above structure, the impedance R of the vibrating beam 12 increases according to the natural frequency. This impedance R is
It can be expressed as

R ≒ (1/222) ・ (1 / (Egγ) ^1/2 ) ・ (AB ² l ² / bh ² ) ・ Q + R ₀ where E: Modulus of elasticity g; Gravity acceleration γ; Density of material A; constant determined by vibration mode B; magnetic flux density l; length of vibrating beam b; width of vibrating beam h; thickness of vibrating beam Q; sharpness of resonance R ₀ ; DC resistance value For example, since the Q of the vibrating beam has a value of several hundreds to several tens of thousands, a large amplitude signal can be obtained as the output of the amplifier in the resonance state.

The processing means and shape of the vibrating beam are not limited to those in this embodiment. For example, B (boron) is diffused in an n-type silicon substrate at 4 × 10 ¹⁹ atoms / cm ³ or more and formed by selective etching. May be used.

However, in such a device, although the back electromotive force generated in the vibrating beam 12 is detected by using the AC bridge, it is practically impossible to completely suppress the input signal component by the AC bridge. Because of this, some of the input components come on the bridge output.

For this reason, the S / N ratio is poor and a stable output signal cannot be obtained.

In order to solve such a problem, the applicant of the present application
Japanese Patent Application No. 62-271557 filed on October 27, 62 "Title of Invention;
"Mechanical filter" is applied.

Hereinafter, this application will be described with reference to FIGS. 8 to 11.

FIG. 8 is an explanatory view of the principle essential structure of an embodiment of Japanese Patent Application No. 62-271557.

In the figure, the same symbols as those in FIG. 5 represent the same functions.

 Hereinafter, only differences from FIG. 5 will be described.

30 is the oscillator body. Both ends of the oscillator body 30 are substrates 11
The first oscillator 31 and the second oscillator fixed to the
The vibrator 32 and the connecting beam motion 33 that mechanically connects the antinode portions of the vibrations of the first vibrator 31 and the second vibrator 32 to each other.

40 is a direct current magnetic field orthogonal to the oscillator body 30 is applied by the magnet 13 and an alternating current is applied to both ends of the first oscillator 31 by the input transformer 41 to cause the oscillator body 30 to move in a direction orthogonal to the magnetic field and the current by the magnetic induction action. It is an exciting means for exciting.

The primary side of the input transformer 14 is connected to the input terminal 42. The secondary side is connected to both ends of the first vibrator 31.

Reference numeral 50 is a vibration detecting means for detecting an electromotive force generated at both ends of the other second vibrator 32. In this case, the output transformer
51 is used. The primary side of the output transformer 51 is connected to both ends of the second oscillator 32, and the secondary side is connected to the output terminal 53 via the amplifier 52.

In the above configuration, the vibrator body 30 is excited by the input signal input to the excitation means 40. The vibration of the vibrator body 30 is detected by the vibration detecting means 50 and taken out as an output signal.

As a result, the vibrator main body 30 becomes the first vibrator 31 for excitation.
And the second beam 32 for electromotive force detection, and the connecting beam 33
Since the antinode portion of the vibration of the first oscillator 31 is coupled, it is electrically separated, but mechanically coupled, so a high input component removal ratio (SN ratio) is obtained. ) Is obtained.

9 is an actual example of the vibrator main body 30, and FIG. 10 is a sectional view taken along line BB in FIG.

In FIG. 10, the oscillator main body 30 is the Q of the oscillators 31 and 32.
To increase the value, cover the transducer body 30 with shell 60,
A state in which the vacuum chamber 61 is enclosed by providing a gap 62 on the peripheral surfaces of the vibrators 31 and 32 is shown.

In FIGS. 8 and 9, for the sake of clarity,
Ciel 60 is not shown.

Such a device is manufactured, for example, by a manufacturing process as shown in FIG.

(1) As shown in FIG. 11 (A), n-type silicon (10
A silicon oxide or silicon nitride film 101 is formed on a substrate 11 that has been cut to the 0) plane. The required portion 102 of the film 101 is removed by photolithography.

(2) Hydrogen (H ₂ ) at 1050 ℃ as shown in Fig. 11 (B)
Etching is performed with hydrogen chloride in an atmosphere to etch a required portion 102 of the substrate 11 to undercut the film 101 to form a recess 103.

Instead of hydrogen chloride, high temperature steam or oxygen may be used, or anisotropic etching with an alkali solution at 40 ° C to 130 ° C may be used.

(3) Hydrogen (H ₂ ) at 1050 ℃ as shown in Fig. 11 (C)
A selective epitaxial growth method is performed by mixing hydrogen chloride (HCl) gas into a source gas in an atmosphere.

That is, by using P-type silicon with a boron concentration of 10 ¹⁸ cm ^-3 ,
The first epitaxial layer 104 corresponding to the lower half of 62 is selectively epitaxially grown.

By using P-type silicon having a boron concentration of 3 × 10 ¹⁹ cm ⁻³ or more, a required portion 102 is formed on the surface of the first epitaxial layer 104.
The second epitaxial layer 105 corresponding to the oscillator main body 30 is selectively epitaxially grown so as to close the substrate.

A third epitaxial layer 106 corresponding to the upper half of the gap 62 is selectively epitaxially grown on the surface of the second epitaxial layer 105 using P-type silicon having a boron concentration of 10 ¹⁸ cm ^-3 .

A fourth epitaxial layer 107 corresponding to the shell 60 is selectively epitaxially grown on the surface of the third epitaxial layer 106 with P-type silicon having a boron concentration of 3 × 10 ¹⁹ cm ⁻³ or more.

(4) As shown in FIG. 11 (D), a silicon oxide or silicon nitride film 101 is formed with hydrofluoric acid (HF).
Etching to remove it, and an etching injection port 108 is provided.

(5) As shown in FIG. 11 (E), a substrate is provided for the fourth layer.
A positive pulse is applied to 11 to inject the etchant 108.
More alkaline solution to inject the first epitaxial layer 104
Then, the third epitaxial layer 106 is removed by selective etching.

Second epitaxial layer 105 and first epitaxial layer 104
Alternatively, the etching action is different from that of the third epitaxial layer 106 because the etching action is suppressed when the boron concentration is 3 × 10 ¹⁹ cm ⁻³ or more.

This is shown, for example, in Fig. 8 on page 123 of "Transducers '87" published by The Institute of Electrical Engineers of Japan.

(6) Hydrogen (H ₂ ) at 1050 ℃ as shown in Fig. 11 (F)
In which n-type silicon is epitaxially grown to
Epitaxial layer 105, fourth epitaxial layer 107, and substrate
The fifth epitaxial layer 10 made of n-type silicon is formed so as to cover the surface of the recessed portion 103 side of 11 and close the injection port 108.
Form 9 and close etching inlet 108.

<Problems to be Solved by the Invention> However, in such a device, the first oscillator 3
1, the connecting portion between the second oscillator 32 and the connecting beam 33 becomes complicated,
Since the epitaxial growth differs depending on the crystal orientation, the crystal formation at the bonding portion cannot be performed neatly. Further, there is a problem that the gap 62 between the shell 60 and the first vibrator 31 and the second vibrator 32 becomes narrower, which causes a problem that the manufacturing yield is deteriorated.

 The present invention solves this problem.

An object of the present invention is to provide an inexpensive mechanical filter that can obtain a stable output signal with a good S / N ratio.

<Means for Solving Problems> In order to achieve this object, the present invention provides a vibrator main body made of a silicon material provided on a silicon substrate, and an exciting means for exciting the vibrator main body. In a mechanical filter comprising a vibration detecting means for detecting an excited vibration of the vibrator body, both ends are integrally formed and fixed to the substrate by a manufacturing process and arranged in parallel with each other, and have a length, a width and a thickness of substantially the same. An oscillator main body made of silicon, which has the same first oscillator and second oscillator, and a direct current magnetic field orthogonal to the oscillator main body is applied to cause an alternating current to flow at both ends of the first oscillator to vibrate by a magnetic induction action. A mechanical fill comprising: an exciting means for exciting the child in a direction orthogonal to the magnetic field and the current; and a vibration detecting means for detecting an electromotive force generated at both ends of the second vibrator. It is obtained by configuring the over.

<Operation> In the above configuration, the vibrator is applied with an alternating magnetic field so as to be orthogonal to each other.

When an input alternating current is applied to both ends of the first vibrator, it is excited in a direction orthogonal to the magnetic field and the current due to the magnetic induction effect.

In this case, the vibration frequency is the natural frequency determined by the length, width, thickness and tension of the first vibrator.

At this time, if the second oscillator also has the same shape and tension,
Because of having the same natural frequency, the excited vibrational energy of the first oscillator is transmitted through the walls at both ends of the first oscillator, and the second oscillator also vibrates at the same frequency.

The vibration of the vibrator body is detected by the vibration detecting means, and its frequency is taken out as an output signal.

 Hereinafter, detailed description will be given based on examples.

<Embodiment> FIG. 1 is an explanatory view of a main part configuration of an embodiment of the present invention.
The figure is an actual use example, FIG. 3 is a sectional view taken along the line BB of FIG. 2, and FIG. 4 is an operation explanatory diagram of FIG.

In the figure, the same symbols as those in FIG. 8 represent the same functions.

 Only parts different from FIG. 8 will be described below.

The difference from FIG. 8 is only that there is no connecting beam 33 connecting the first vibrator 31 and the second vibrator 32.

Then, the first vibrator 31 and the second vibrator 32 are provided close to each other, and are formed to have the same length, width, and thickness.

In addition, the substrate 11, the first oscillator 31, and the second oscillator 32 are
As shown in FIG. 11, it is made of silicon and is integrally formed by a manufacturing process.

In the above configuration, the vibrators 31 and 32 are applied with an alternating magnetic field so as to be orthogonal to each other,
When an input alternating current is applied to both ends of the first oscillator 31, it is excited in a direction orthogonal to the magnetic field and the current due to the magnetic induction effect.

In this case, the vibration frequency is the natural frequency determined by the length, width, thickness and tension of the first vibrator.

At this time, if the second oscillator 32 also has the same shape and the same tension, it has the same natural frequency, so that the vibrating energy of the excited first oscillator 31 is the substrate at both ends of the first oscillator 31. 11
And the second oscillator 32 also vibrates at the same frequency.

The vibration of the second vibrator 32 is detected by the vibration detecting means, and its frequency is taken out as an output signal.

As a result, (1) the vibrator body 30 has only two vibrators 31 and 32, and since the connecting beam 33 as in the conventional example of FIG. 8 is eliminated,
The manufacturing process yield is greatly improved.

(2) The vibrator main body 30 includes a first vibrator 31 and a second vibrator 32, both ends of which are integrally formed and fixed to the substrate 11 by a manufacturing process and are arranged in parallel with each other and have substantially the same length, width, and thickness. Since it is made of silicon, the first oscillator for excitation 31
And the second oscillator 32 for electromotive force detection, which is electrically separated but mechanically coupled,
A high input component removal ratio (S / N ratio) can be obtained.

(3) As shown in FIG.
When strain ε ₀ is applied in the direction perpendicular to the axis of 2, the conventional oscillator main body 30 has the connecting beam 33, so that FIG.
The first oscillator 31 and the second oscillator 32 are deformed as shown by the broken line
There was a problem that the natural frequency of was changed. But,
In the present invention, the deformation as shown by the broken line in FIG. 4 (B) occurs and no error occurs.

(4) Since the first oscillator 31 and the second oscillator 32 are made of silicon and can be formed integrally with the substrate 11 by the manufacturing process, the first oscillator 31, the second oscillator 32, and the substrate 11 are Is a silicon-based mechanical filter with good temperature characteristics.

(5) Since the first oscillator 31 and the second oscillator 32 are made of silicon and can be configured integrally with the substrate 11 by the manufacturing process, the configuration can be simplified and an inexpensive mechanical filter can be obtained.

(6) Since the first oscillator 31 and the second oscillator 32 are made of silicon and can be formed integrally with the substrate 11 by the manufacturing process, the accuracy obtained in the manufacturing process is broken, and the first oscillator 31 and It is possible to obtain a mechanical filter having good accuracy in the mutual spacing and directional position of the second oscillators 32, and to obtain a mechanical filter with improved performance.

<Effects of the Invention> As described above, according to the present invention, a vibrator main body made of a silicon material provided on a silicon substrate, an excitation means for exciting the vibrator main body, and an excitation of the vibrator main body. In a mechanical filter including a vibration detecting unit for detecting a vibration, both ends of the first filter are formed and fixed to the substrate in a monolithic structure by a manufacturing process and arranged in parallel with each other, and the first vibrator and the first vibrator have substantially the same length, width and thickness. A vibrator body made of silicon and provided with two vibrators, and a direct current magnetic field orthogonal to the vibrator body is applied to cause an alternating current to flow through both ends of the first vibrator so that the vibrator is orthogonal to the magnetic field and the current by a magnetic induction action. A mechanical filter comprising: an excitation unit that excites in a direction of vibration and a vibration detection unit that detects an electromotive force generated at both ends of the second oscillator.

As a result, (1) The shape of the vibrator body is only two vibrators, and since the connecting beam as in the conventional example is eliminated, the yield of the manufacturing process is significantly improved.

(2) The vibrator body is made of silicon and has a first vibrator and a second vibrator, both ends of which are integrally formed and fixed to the substrate by a manufacturing process, arranged in parallel with each other, and having substantially the same length, width, and thickness. Therefore, it is divided into a first oscillator for excitation and a second oscillator for electromotive force detection, which are electrically separated but mechanically coupled, so that a high input component removal ratio ( S / N ratio) is obtained.

(3) When strain is applied to the oscillator body in a direction perpendicular to the axis of the oscillator, in the oscillator body of the conventional example, the natural vibration of the first oscillator and the second oscillator occurs due to the existence of the connecting beam. Although there is a problem that the number changes, the present invention does not cause an error.

(4) Since the first oscillator and the second oscillator are made of silicon and can be integrally formed with the substrate by the manufacturing process, the first oscillator, the second oscillator, and the substrate are made of silicon. A mechanical filter having good temperature characteristics can be obtained.

(5) The first oscillator and the second oscillator are made of silicon,
Since it was possible to configure it integrally with the substrate by the manufacturing process,
The structure can be simplified and an inexpensive mechanical filter can be obtained.

(6) The first oscillator and the second oscillator are made of silicon,
Since it was possible to configure it integrally with the substrate by the manufacturing process,
The accuracy obtained in the manufacturing process is broken, the distance between the first vibrator and the second vibrator is good, and the accuracy of the directional position is good, and a mechanical filter with improved performance is obtained.

Therefore, according to the present invention, a stable output signal having a good S / N ratio can be obtained, and an inexpensive mechanical filter can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principal part configuration of an embodiment of the present invention, FIG. 2 is an explanatory view of the essential part configuration of an actual use example, and FIG. 3 is a sectional view taken along line BB in FIG. FIG. 5 is an explanatory view of the operation of FIG. 1, FIGS. 5 to 7 are explanatory views of the configuration of a conventional example that is generally used in the past, FIG. 5 is an explanatory view of the configuration of essential parts, and FIG. 7 is a sectional view taken along line AA of FIG.
FIGS. 8 to 11 are explanatory views of the construction of Japanese Patent Application No. 62-271557. 11 ... Substrate, 13 ... Magnet, 30 ... Vibrator main body, 31 ... First oscillator, 32 ... Second oscillator, 40 ... Excitation means, 41 ...
Input transformer, 42 ... input terminal, 50 ... vibration detection means,
51 …… output transformer, 52 …… amplifier, 53 …… output terminal,
60 …… Ciel, 61 …… Vacuum chamber, 62 …… Gap.

Front page continued (72) Inventor Takashi Kobayashi 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Inventor Tetsuya Watanabe 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. In-house (72) Inventor Nao Nishikawa 2-9-32 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) In-house Takashi Yoshida 2-9-32 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (56) References Japanese Patent Laid-Open No. 47-26056 (JP, A) Japanese Patent Laid-Open No. 55-64417 (JP, A) Japanese Utility Model Laid-Open No. 61-50331 (JP, U)

Claims (1)

(57) [Claims] 1. A vibrator main body made of a silicon material provided on a silicon substrate, an exciting means for exciting the vibrator main body, and a vibration detecting means for detecting an excited vibration of the vibrator main body. In the mechanical filter provided, the both ends are integrally formed and fixed to the substrate by a manufacturing process by a manufacturing process, are arranged in parallel with each other, and are provided with a first oscillator and a second oscillator, and a vibration made of silicon is provided. A sub-body, excitation means for applying a direct-current magnetic field orthogonal to the oscillator body, and causing an alternating current to flow through both ends of the first oscillator to excite the oscillator in a direction orthogonal to the magnetic field and the current by a magnetic induction action; And a vibration detecting means for detecting an electromotive force generated at both ends of the second vibrator.