JPH0238934A - Vibration type semiconductor transducer - Google Patents

Abstract

PURPOSE:To enable high-S/N, stable self-oscillation by exciting a 1st vibrator and transmitting its vibration to a 2nd vibrator, and enabling a vibrator main body to excite and vibrate itself. CONSTITUTION:When an AC magnetic field is applied so as to cross the vibrators 31 and 32 to make an AC current flow to both ends of the 1st vibrator 13, the vibrators are excited through magnetic induction at right angles to the magnetic field and current. At such a time, the vibration frequency is a natural vibration frequency determined by the length, width, thickness, and tension of the 1st vibrator. The vibration energy of the 1st vibrator 31 is transmitted through the walls at both ends of the 2nd vibrator 31 and the 2nd vibrator 32 also vibrates at the same vibration frequency. The vibration of the 2nd vibrator 32 is detected by a vibration detecting means 50 and its frequency is sent out as an output signal and also fed back to an input transformer 41.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> 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 the change in the vibration frequency that occurs in the vibrating beam in response to a force applied to the substrate or a change in the environment. The present invention relates to a type transducer.

More specifically, the present invention relates to an inexpensive vibrating semiconductor transducer that has a high S/N ratio, can stably generate self-oscillation, and is inexpensive.

<Prior art> Figures 5 to 8 are from the patent application filed on June 6, 1988.
-131.456 “Vibrating semiconductor transducer”
FIG. 2 is a configuration explanatory diagram of an embodiment of the present invention.

Fig. 5 is a perspective view of a configuration using a vibrating transducer as a pressure sensor, Fig. 6 is an enlarged plan view of part A in Fig. 5 with electrical wiring, and Fig. 7 is a diagram showing A in Fig. 6. -A cross-sectional view, Figures 8 (A) and (B) are diagrams showing Figure 6 as electrical circuits, and Figure 8 (B) shows a reverse bias voltage applied between the p-type layer and the n+ type layer. The power source for applying the voltage is shown.

In these figures, 10 has a (100) plane, for example, an impurity concentration 10'
! It is a P-type silicon substrate of less than atomic/cm'.

A diaphragm 11 is formed on one surface of this silicon substrate 10 by etching.

An n4 diffusion layer (not shown in the figure) with an impurity concentration of about 1017 is partially formed on the surface of the diaphragm 11 (the surface that is not etched), and a vibration beam 1 is partially formed on this n+ diffusion layer.
2 is formed in the <001> direction.

Note that this vibration am12 processes the n1 layer and the second layer formed on the diaphragm 11 using photolithography and under-etching techniques.

13 is located approximately at the upper center of the vibrating beam 12 and is perpendicular to the vibrating beam 12;
In addition, the magnet is provided in a non-contact state.

14 is an 8102 film (see FIG. 7) as an insulating film.

15a and 15b are metal electrodes such as aluminum, and one end of this metal electrode 15a is connected to the n10 layer extending from the vibrating beam 12 through a contact hole 16a provided in the 5i02 layer, and the other end is connected via a lead wire. It is connected to a comparison resistor R0 whose resistance value is approximately equal to the resistance value of the vibrating beam 12 and to one end of the amplifier 20.

The output of the amplifier 20 is taken out as an output signal, branched off, and connected to one end of the primary coil L. The other end of this coil L1 is connected to a common line.

On the other hand, the other end of the comparison resistor R0 is connected to the other end of the secondary coil L2 whose midpoint is connected to the common line, and the other end of this secondary coil L2 is formed at the #1 end of the vibrating beam 12 in the same manner as described above. The metal electrode 15b is connected to the metal electrode 15b.

In the above configuration, the P type NJ (substrate 10) and the n+ type layer (
applying a reverse bias voltage between the vibrating beams 12) to insulate them;
When an alternating current i is applied to the vibrating beam 12, the impedance of the vibrating beam increases due to electromagnetic induction at the resonant frequency of the vibrating beam 12, and the comparison resistor R0 and the midpoint are connected to the common line.

An unbalanced signal can be obtained by the bridge configured by This signal is amplified by an amplifier 20, coiled,
When positive feedback is given to , the system automatically oscillates at the natural frequency of the vibrating beam 12.

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

R Ki (1/222) ・ (1/(Eg γ )
Electricity/2 ) (AB'!'/bh' )・Q+R0 Here, E; Elastic modulus g: Gravitational acceleration γ; Density A of the material making up the vibrator; Constant B determined by the vibration mode; Magnetic flux density! ; Length of the vibrating beam b: Width of the vibrating beam h: Thickness of the vibrating beam Q; Sharpness of resonance Ro; DC resistance value According to the above formula, the Q of the vibrating beam takes a value of several hundreds to tens of thousands.
A large amplitude signal can be obtained as the output of the amplifier in the resonant state. In this way, if the oscillating semiconductor transducer amplifier is configured to have sufficient gain to provide positive feedback, the system will self-oscillate at its natural frequency.

However, in such a device, although the back electromotive force generated in the vibrating beam 12 is detected using an AC bridge, it is virtually impossible to completely suppress the excitation component of the excitation current with an AC bridge. Therefore, the wJ lightning current component is added to the bridge output.

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

In order to solve these problems, the applicant of the present application
Patent Application No. 62-272653 filed on October 28, 2017
The title of the invention is: "Vibrating Transducer".

This application will be explained below with reference to FIGS. 9 to 12.

FIG. 9 is a diagram illustrating the basic structure of an embodiment of Japanese Patent Application No. 62-272653.

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

Hereinafter, only the differences from FIG. 5 will be explained.

30 is a vibrator main body. The vibrator main body 30 has both ends fixed to the substrate 11 and has first vibrators 31 arranged parallel to each other.
．． It includes a connecting beam 33 that mechanically couples the antinode portions of the second vibrator 32, the first vibrator 31, and the second S vibrator 32 to each other.

Reference numeral 40 applies a direct current magnetic field perpendicular to the vibrator body 30 using the magnet 13, and causes an AC current to flow through the input cadence 41 at both ends of the first vibrator 31, thereby causing the vibrator body 30 to move by magnetic induction.
This is an excitation means that excites the magnetic field in a direction perpendicular to the magnetic field and the current.

The input cadence 41 has a secondary side connected to both ends of the first @ mover 31.

Reference numeral 50 denotes vibration detection means for detecting the electromotive force generated at both ends of the second vibrator 32. In this case, the output Lance 51
, an amplifier 52 are used.

The primary side of the output transformer 51 is connected to both ends of the second vibrator 32, and 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. There is.

In the above configuration, the vibrator main 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 detection means 50 and taken out as an output signal. 'As a result, the vibrator main body 30 is divided into the first vibrator 31 for rotation and the second vibrator 32 for electromotive force detection, and the connecting beam 33 connects the first @ vibrator 31 and the second vibrator 32. Since the antinodes of the vibrations of flI are coupled together, they are electrically separated, but mechanically coupled, resulting in a high excitation component removal ratio (S/
N ratio) is obtained.

FIG. 10 shows an actual example of the vibrator main body 30, and FIG. 11 shows the first
It is a BB sectional view of figure 0.

In FIG. 11, the vibrator body 30 includes a vibrator 31.3.
In order to increase the Q value of the transducer body 3 with a shell 60,
0 is covered, a gap 62 is provided on the circumferential surface of the vibrator 31, 32, and the vibrator 31, 32 is sealed in a vacuum chamber 61.

In Figures 9 and 10, for the sake of clarity,
Shell 60 is not shown.

Such a device can be made, for example, as shown in FIG.

(1) As shown in Figure 12 (A), n-type silicon (1
A film 101 of silicon oxide or silicon nitride is formed on the substrate 10 cut into the 00) plane. Membrane 101
Required portions 102 of are removed by photolithography.

(2) As shown in FIG. 12(B), etching is performed with hydrogen chloride in a hydrogen (H2) atmosphere at 1050° C. to etch the required portions 102 on the substrate 1 to undercut the film 101 and create recesses. 103 is formed.

Note that instead of hydrogen chloride, high-temperature steam or oxygen may be used, or anisotropic etching may be performed using an alkaline solution at a temperature of 40 DEG C. to 130 DEG C.

(3) As shown in Figure 12 (C), hydrogen chloride (HCl2) is used as the source gas in a hydrogen (H2) atmosphere at 1050°C.
A selective epitaxial growth method is performed by mixing gas.

That is, ■ P-type silicon with a boron concentration of 10"cm-2,
First epitaxial layer 1 corresponding to the lower half of the gap 62
04 is selectively epitaxially grown.

(2) A second epitaxial layer 105 corresponding to the vibrator main body 30 is selectively epitaxially grown on the surface of the first epitaxial layer 104 using P-type silicon with a boron concentration of 3×10 cm − , so as to cover the required portions 102 .

(2) 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 Nj 105 using P-type silicon with a boron concentration of 10'''cm''2.

■A shell 60 is formed on the surface of the third epitaxial layer 106 by P-type silicon with a boron concentration of 3×10”am”2.
A fourth epitaxial layer 107 corresponding to 107 is selectively epitaxially grown.

(4) As shown in FIG. 12(D), silicon oxide,
Alternatively, the silicon nitride film 101 may be coated with hydrofluoric acid (
HF) to remove the etching inlet 10.
8 will be provided.

(5) As shown in FIG. 12(E), a positive pulse is applied to the substrate 10 for the fourth layer, and alkaline solution is injected from the etching solution injection port 108 to form the first epitaxial layer 104. Third epitaxial layer 106 is selectively etched and removed.

Second epitaxial layer 105 and first epitaxial layer 1
04 or the third epitaxial layer 106 because the boron concentration is 3X10I.
This is because when the value exceeds "gcm-", the etching action is inhibited.

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

(6) As shown in FIG. 12(F), epitaxial growth of n-type silicon is performed in hydrogen (H2) at 1050'C, and the second epitaxial layer 105, the fourth epitaxial layer 107, and the recess 103 side of the substrate 1 are grown. In addition to covering the surface of
A fifth epitaxial layer [109] made of n-type silicon is formed so as to close the injection port 108, and the etching injection port 108 is closed.

<Problem to be solved by the invention> However, in such a device, the first vibrator 31
．． The joint part between the second vibrator 32 and the connecting beam 33 is complicated, and epitaxial growth differs depending on the crystal orientation, so crystal formation at the joint part cannot be performed neatly. Gap 6 between vibrator 32
There were problems such as the width of 2 becoming narrower, and there was a backlog that worsened the manufacturing yield.

The present invention solves this problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vibrating semiconductor transducer that has a high S/N ratio, can stably cause automatic oscillation, and is inexpensive.

Means for Solving the Problems In order to achieve this object, the present invention provides a vibrator body made of a silicon single crystal material provided on a silicon single crystal substrate, and a method for exciting the vibrator body. A vibrating semiconductor transducer comprising an excitation means and a vibration detection means for detecting the excited vibration of the vibrator body, wherein both ends are fixed to the substrate and are arranged parallel to each other, and the length, width and thickness are A vibrator body is provided with a first vibrator and a second vibrator that are substantially equal, and a direct current magnetic field orthogonal to the vibrator body is applied, and an alternating current is caused to flow across both ends of the first vibrator to cause the vibrator to move by magnetic induction. It is equipped with an excitation means that excites in a direction orthogonal to the magnetic field and the current, an amplifier that detects the electromotive force generated at both ends of the second vibrator, and provides a gain necessary for self-excitation, and a filter that provides a necessary phase. and vibration detecting means configured to sustain self-excited oscillation at the natural frequency of the vibrator body.

Effect〉 In the above configuration, an external force is applied to the substrate.

When an alternating current magnetic field is applied orthogonally to the vibrator and an alternating current is passed through both ends of the first vibrator, due to the magnetic induction effect,
Excite in the direction perpendicular to the magnetic field and current.

At this time, the vibration frequency is excited at a natural frequency determined by the length, width, thickness, and tension of the first vibrator.

At this time, if the second vibrator has the same shape and the same tension, it will have the same natural frequency, so the vibration energy of the excited first vibrator will be transmitted through the walls at both ends of the first vibrator. The second vibrator also vibrates at the same frequency.

The vibration of the vibrator body is detected by the vibration detection means, and its frequency is extracted as an output signal.

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

Hereinafter, a detailed explanation will be given based on examples.

<Example> Fig. 1 is an explanatory diagram of the main part configuration of an embodiment of the present invention, Fig. 2 is an actual usage example, Fig. 3 is a sectional view taken along line B-8 in Fig. 2, and Fig.
The figure is an explanatory diagram of the operation of FIG. 1.

In the figure, structures with the same symbols as in FIG. 9 represent the same functions.

Hereinafter, only the differences from FIG. 9 will be explained.

The only difference from FIG. 9 is that there is no connecting beam 33 connecting the first @ mover 31 and the second vibrator 32.

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

In the above configuration, an external force is applied to the substrate 1.

When an alternating current magnetic field is applied orthogonally to the vibrators 31 and 32 and an alternating current is passed through both ends of the first vibrator 31, the vibrators 31 and 32 are excited in a direction perpendicular to the magnetic field and the current due to magnetic induction.

At this time, the length and width of the gil dynamic frequency first oscillator,
Excite with natural frequency determined by thickness and tension.

At this time, when the second vibrator 32 has the same shape and the same tension, the vibration energy of the excited first vibrator 31 is transmitted to the walls at both ends of the first vibrator 31, since they have the same natural frequency. The second vibrator 32 also vibrates at the same frequency.

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

As a result, the external force applied to the substrate 1 can be detected.

(1) The shape of the vibrator main body 30 is that of two vibrators 31°32
Since the connecting beam 33 as in the conventional example shown in FIG. 9 is eliminated, the yield of the manufacturing process is greatly improved.

(2) The first vibrator 31 through which excitation current flows and the second vibrator 3
2 is completely electrically insulated, so a high excitation component removal ratio (S/N ratio) can be obtained.

(3) Strain ε is applied to the vibrator body 30 in a direction perpendicular to the axis of the vibrator 31, 32, as shown in FIG.

(For example, strain generated under static pressure), in the conventional vibrator main body 30, due to the connecting beam 33, as shown in FIG. 4(A).
deformation as shown by the broken line occurs, and the first vibrator 31. There was a problem in that the natural frequency of the second vibrator 32 changed.

However, in the present invention, deformation as shown by the broken line in FIG. 4(B) occurs and no error occurs.

The above transducer's vibration frequency changes depending on the temperature coefficient of silicon's elastic modulus, so in addition to being used as a pressure gauge, it can also be used as a thermometer by storing it in a vacuum container, and also as a density meter. .

<Effects of the Invention> As explained above, the present invention provides a vibrator body made of a silicon single crystal material provided on a silicon single crystal substrate, an excitation means for exciting the vibrator body, and the vibrator body. A vibrating semiconductor transducer comprising: a vibration detecting means for detecting excited vibrations of a main body; A vibrator body comprising a second vibrator; a DC magnetic field orthogonal to the vibrator body is applied, an alternating current is passed through both ends of the first vibrator, and the vibrator is moved in a direction perpendicular to the magnetic field and current by magnetic induction; The device includes an excitation means for exciting, an amplifier for detecting the electromotive force generated at both ends of the second vibrator and giving a gain necessary for self-oscillation, and a filter for giving a necessary phase, and detecting the electromotive force generated at both ends of the second vibrator, and a filter giving a necessary phase. A vibrating semiconductor transducer is constructed, comprising a vibration detecting means configured so that automatic oscillation continues for several times.

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

Therefore, (1) Since the shape of the vibrator main body is reduced to only two vibrators, and there is no connecting beam as in the conventional example, the yield of the manufacturing process is greatly improved.

(2) Since the first vibrator through which the excitation current flows and the second vibrator are completely electrically insulated, a high excitation component removal ratio (S/N ratio) can be obtained.

(3) When a strain (for example, strain generated under static pressure) is applied to the transducer body in a direction perpendicular to the axis of the transducer, in the conventional transducer body, the first vibration occurs due to the connecting beam. There was a problem in that the natural frequency of the second child oscillator changed.

However, the present invention does not introduce any errors.

Therefore, according to the present invention, it is possible to realize an inexpensive vibrating semiconductor transducer that has a high S/N ratio, can stably cause self-oscillation, and is inexpensive.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle main part configuration of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the main part composition of an example of actual use, and Fig. 3 is a diagram showing the B-8 4 is an explanatory diagram of the operation of FIG. 1, FIGS. 5 to 8 are explanatory diagrams of the configuration of a conventional example commonly used, and FIG. 5 is a perspective view of the transducer configured as a pressure gauge. Figure 6 is an enlarged plan view of part A in Figure 5 with electrical wiring, Figure 7 is a sectional view taken along line A-A in Figure 6, and Figure 8 is an electrical circuit diagram of Figure 6. , and FIGS. 9 to 12 are explanatory diagrams of the structure of Japanese Patent Application No. 62-272653. 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, 60... Shell, 61...
Vacuum chamber, 62... gap. Figure 1 Figure 3 Figure 4 Figure 2 (A) Figure 5 1P Figure 6 Figure 9 Figure 10 Figure 7 Single 8 Figure (A3 Figure 11)

Claims (1)

[Scope of Claims] A vibrator body made of a silicon single crystal material provided on a silicon single crystal substrate, an excitation means for exciting the vibrator body, and detecting the excited vibration of the vibrator body. A vibrating semiconductor transducer comprising: a vibrating semiconductor transducer comprising a first vibrator and a second vibrator having both ends fixed to the substrate, arranged parallel to each other, and having substantially equal length, width, and thickness; , an excitation unit that applies a DC magnetic field perpendicular to the vibrator body and flows an AC current to both ends of the first vibrator to excite the vibrator in a direction perpendicular to the magnetic field and the current by magnetic induction; and the second vibrator. The vibrator is configured to detect the electromotive force generated at both ends of the vibrator, and is equipped with an amplifier that provides the gain necessary for self-oscillation, and a filter that provides the necessary phase, so that the self-oscillation is sustained at the natural frequency of the vibrator body. A vibrating semiconductor transducer comprising vibration detecting means.