JPH0756466B2 - Vibration type semiconductor transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a vibrating semiconductor transducer.

The present invention vibrates a vibrating beam formed on a silicon substrate at the natural frequency of the vibrating beam, and detects a change in vibration frequency that occurs in the vibrating beam in response to a force applied to the substrate or a change in environment. Shape transducer.

More specifically, the present invention relates to a vibrating semiconductor transducer having a high S / N ratio and capable of stably causing self-excited oscillation.

<Prior Art> FIGS. 5 to 8 show Japanese Patent Application No. 61-131 filed on June 6, 1986.
It is a structure explanatory view of one Example of No. 456 "vibration type semiconductor transducer". FIG. 5 is a perspective view of a structure using a vibration type transducer as a pressure sensor, FIG. 6 is an enlarged plan view of a portion A in FIG. 5 with electric wiring, and FIG. 7 is AA of FIG. A cross-sectional view, FIGS. 8 (A) and 8 (B), shows a sixth view.
FIG. 8 is a diagram showing an electric circuit, and FIG. 8 (B) shows a power supply for applying a reverse bias voltage between the p-type layer and the n ^{+ -type} layer.

In these figures, 10 is a p-type silicon substrate having a {100} plane, for example, an impurity concentration of 10 ¹⁵ atoms / cm ³ or less. The diaphragm 11 is formed on one surface of the silicon substrate 10.
Are formed by etching. This diaphragm
An n ⁺ diffusion layer (not shown in the figure) with an impurity concentration of about 10 ¹⁷ is partially formed on the surface of 11 (the surface that is not etched).
The vibrating beam 12 is formed in the <001> direction on a part of the n ⁺ diffusion layer. The vibrating beam 12 is formed by processing the n ⁺ layer and the p layer formed on the diaphragm 11 by using photolithography and under etching techniques.

13 is orthogonal to the vibrating beam 12 approximately above the center of the vibrating beam 12, and
Magnet provided in a non-contact state, 14 is Si as an insulating film
It is an O ₂ film (see FIG. 7). 15a and 15b are metal electrodes such as Al, one end of which is connected through a contact hole 16a provided in the SiO ₂ layer to the n ⁺ layer extending from the vibrating beam 12, and the other end through a lead wire. Is connected to one end of a comparison resistor R ₀ and an amplifier 20, 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 15
connected to b.

In the above structure, the p-type layer (substrate 10) and the n ^{+ -type} layer (vibrating beam)
12) Applying a reverse bias voltage between
When an AC current i is applied to the vibrating beam 12, the impedance of the vibrating beam increases at the resonance frequency of the vibrating beam 12 due to electromagnetic induction.
An unbalanced signal can be obtained by the bridge composed of the comparison resistor R ₀ and L ₂ whose middle point is connected to the common line. When this signal is amplified by the amplifier 20 and is positively fed back to the coil L ₁ , the system self-oscillates at the natural frequency of the vibrating beam 12.

In the above structure, the impedance R of the vibrating beam 12 increases according to the natural frequency. This impedance R can be expressed by the following equation.

R ≒ (1/222) ・ (1 / (Egr) ^1/2 ) ・ (AB ² l ² / bh ² ) ・ Q + R ₀ where E: Elastic modulus g; Gravity acceleration r; 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, the Q of the vibrating beam takes a value of hundreds to tens of thousands,
In the resonance state, a large amplitude signal can be obtained as the output of the amplifier. In this way, if the gain of the vibration type semiconductor transducer amplifier is sufficiently taken and positive feedback is performed, the system self-oscillates at the natural frequency.

<Problems to be Solved by the Invention> However, in such a device, although the counter electromotive force generated in the vibrating beam 12 is detected by using the AC bridge, the exciting component of the exciting current is detected by the AC bridge. Since it is practically impossible to completely suppress it, an excitation current component is carried on the bridge output.

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

The present invention solves this problem.

An object of the present invention is to provide a vibrating semiconductor transducer having a good S / N ratio and capable of obtaining a stable output signal.

<Means for Solving the Problems> In order to achieve this object, the present invention excites a vibrator body made of a silicon single crystal material provided on a substrate of a silicon single crystal, and the vibrator body. A vibrating semiconductor transducer comprising: an exciting means; and a vibration detecting means for detecting the excited vibration of the vibrator body, wherein two first vibrators, both ends of which are fixed to the substrate and arranged in parallel with each other, A vibrator main body including a second vibrator that mechanically couples the antinode portion of the vibration of the first vibrator, and a DC magnetic field orthogonal to the vibrator main body is applied to both ends or two ends of one first vibrator. Excitation means for applying an alternating current to one end of one of the first oscillators to excite the oscillator in a direction perpendicular to the magnetic field and the current by magnetic induction, and both ends or two of the other first oscillator. The other end of the first oscillator of A self-excited oscillation is maintained at the natural frequency of the vibrator body, which includes an amplifier that gives a gain necessary for detecting the electromotive force generated on the side and self-excites, and a filter that gives a necessary phase. And a vibration detecting means.

<Operation> In the above configuration, when an external force is applied to the substrate, the natural frequency of the vibrator body changes in accordance with the external force. The vibration of the vibrator body is detected by the vibration detecting means, and the frequency is taken out as an output signal.

As a result, the external force applied to the substrate can be detected.

Hereinafter, detailed description will be given based on examples.

<Embodiment> FIG. 1 is an explanatory view of a principal configuration of a principle of an embodiment of the present invention.

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

Only parts different from FIG. 5 will be described below.

30 is the oscillator body. The vibrator main body 30 has two ends fixed to the substrate 11 and arranged in parallel to each other. The first vibrator 31 and the second vibrator 31 mechanically couple the antinodes of the vibration of the first vibrator 31 with each other. 32 and.

40 is a transformer for applying a DC magnetic field orthogonal to the vibrator body 30 by the magnet 13 and inputting an AC current to both ends of the first vibrator 31.
It is an excitation means that is caused to flow by 41 to excite the vibrator body 30 in a direction orthogonal to the magnetic field and the current by the magnetic induction action.

The secondary side of the input transformer 41 is connected to both ends of the one first oscillator 31.

50 is a vibration detecting means for detecting an electromotive force generated at both ends of the other first vibrator 31. In this case, output transformer 5
1, the amplifier 52 is used. The primary side of the output transformer 51 is connected to both ends of the other first oscillator 31, the secondary side is connected to the output terminal 53 via the amplifier 52, and is branched and connected to the primary side of the input transformer 41. Has been done.

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 body 30 has the first vibrator 31 for excitation,
The first oscillator 31 for electromotive force detection is divided into the second oscillator 32.
Thus, since the antinode portion of the vibration of the first oscillator 31 is coupled, it is electrically separated but mechanically coupled, so that the high excitation component removal ratio (S / N ratio) is obtained.

FIG. 2 is an actual example of the vibrator body 30, (A) is a plan view,
(B) is a BB sectional view of (A).

The experimental results are shown in FIG.

The S / N ratio is 30-40 dB.

In the vertical direction of FIG. 3, one scale indicates 5 dB, and the center frequency of the peak value is 71551.1 Hz.

FIG. 4 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

In this embodiment, the secondary side of the input transformer 41 is connected to one same end side of the two first vibrators 31, and the primary side of the output transformer 51 is the same as the other one of the two first vibrators 31. It is connected to the end side.

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

Although the second oscillator 32 is described as being made of P-type silicon in the above embodiment, the present invention is not limited to this.
For example, silicon oxide (SiO ₂ ) or silicon nitride (Si ₃ N ₄ ) may be vapor-deposited with a conductor such as aluminum.

Since the vibration frequency of the transducer changes depending on the temperature coefficient of the elastic modulus of silicon, it can be used not only as a pressure gauge but also as a thermometer by being housed in a vacuum container and also as a density meter.

<Effects of the Invention> As described above, the present invention provides a vibrator main body made of a silicon single crystal material provided on a substrate of a silicon single crystal, an excitation means for exciting the vibrator main body, and the vibrator. A vibration type semiconductor transducer comprising a vibration detecting means for detecting an excited vibration of a main body, in which two first vibrators having both ends fixed to the substrate and arranged in parallel with each other and a vibration of the first vibrator A vibrator main body including a second vibrator mechanically coupling the antinode portion of the first vibrator, and a DC magnetic field orthogonal to the vibrator main body is applied to both ends of one first vibrator or two first vibrators. Excitation means for applying an alternating current to one of the same ends to excite the vibrator by a magnetic induction action in a direction orthogonal to the magnetic field and the current, and one end of the other first vibrator or the other of the two first vibrators. Of electromotive force generated on the same end side of And a vibration detecting means configured to maintain self-oscillation at the natural frequency of the vibrator body, the amplifier including an amplifier that gives a gain necessary for self-excited oscillation and a filter that gives a necessary phase. We have constructed a vibrating semiconductor transducer.

As a result, the oscillator body is divided into a first oscillator for excitation and a first oscillator for electromotive force detection, and the second oscillator is connected to the antinode portion of the vibration of the first oscillator. Because I was told
Since they are electrically separated, but mechanically coupled, a high excitation component removal ratio (S / N ratio) can be obtained.

Therefore, according to the present invention, it is possible to realize a vibrating semiconductor transducer having a good S / N ratio and capable of obtaining a stable frequency output signal.

[Brief description of drawings]

FIG. 1 is an explanatory view of the configuration of a principal part of one embodiment of the present invention, FIG. 2 is an explanatory diagram of the structure of the principal part of FIG. 1, (A) is a plan view,
(B) is a sectional view taken along line BB in (A), FIG. 3 is an explanatory view of the effect of FIG. 1, FIG. 4 is an explanatory view of a main part configuration of another embodiment of the present invention, and FIGS. The figure is a configuration explanatory view of a conventional example generally used from the past. FIG. 5 is a perspective view in which a transducer is used as a pressure gauge, and FIG. 6 is an enlarged plan view of a portion A in FIG. FIG. 7, FIG. 7 is a sectional view taken along line AA in FIG. 6, and FIG. 8 is a view showing FIG. 6 in an electric circuit. 10 …… substrate, 11 …… diaphragm, 13 …… magnet, 30 ……
Vibrator body, 31 …… First vibrator, 32 …… Second vibrator, 40
...... Excitation means, 41 …… Input transformer, 42 …… Input terminal,
50 …… Vibration detection means, 51 …… Output transformer, 52 …… Amplifier, 53 …… Output terminal.

Front page continuation (72) Inventor Tetsuya Watanabe 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Hideki Kuwayama 2-39 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. In-house (72) Takashi Kobayashi 2-9-32 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Co., Ltd. (72) In-house author Sagara Harada 2-9-32 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Co., Ltd. Within

Claims (1)

[Claims] 1. A vibrator main body made of a silicon single crystal material provided on a silicon single crystal substrate, an excitation means for exciting the vibrator main body, and a vibration for detecting the excited vibration of the vibrator main body. In a vibrating semiconductor transducer comprising a detecting means, two first oscillators, both ends of which are fixed to the substrate and arranged in parallel with each other, are mechanically coupled to a vibration antinode portion of the first oscillators. A vibrator main body including a second vibrator and a DC magnetic field orthogonal to the vibrator main body are applied, and an alternating current is applied to both ends of one first vibrator or one end of two first vibrators. The excitation means that excites the oscillator in the direction perpendicular to the magnetic field and the current by the magnetic induction action, and the electromotive force generated at both ends of the other first oscillator or the same end of the other two first oscillators. Gain necessary for detecting and self-exciting A vibration type semiconductor transducer, comprising: an amplifier for applying a desired phase and a filter for providing a required phase, and a vibration detecting means configured to maintain self-excited oscillation at a natural frequency of the vibrator body.