JPH0961453A - Displacement sensor and displacement measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement sensor which is compact, light, and superior, and has a high detection sensitivity and a sound wave/ultrasonic sensor, an acceleration sensor, and an angular velocity sensor using it. SOLUTION: A displacement sensor consists of a center lever 10 and distortion resistance elements 3a, 3b, 4a, and 4b provided on one surface of the lever 10 which is fixed at its both ends. At least two distortion resistance elements are provided near the fixing part of the lever and at least two distortion resistance elements are provided at the center of the lever and a Wheatstone bridge circuit is formed by at least four distortion resistance elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor using a strain resistance element and a doubly supported beam, and particularly to a sound wave / ultrasonic wave,
The present invention relates to a sensor for detecting acceleration, angular velocity, etc. with high sensitivity.

[0002]

2. Description of the Related Art Conventionally, ultrasonic waves, vibrations, accelerations, angular velocities, etc. have been measured by detecting the amount of deformation (strain) of a beam or diaphragm due to an external force, and these have been used as sensors for these (Japanese Patent Laid-Open Publication No. Sho. 59-57595, JP-A-61-2
20598, JP-A-5-93628). A piezoelectric body, an electrostatic capacitance, a strain resistance element, etc. are used for detecting the strain. Among these, the piezoelectric body has high sensitivity, but static strain cannot be detected.The electrostatic capacitance can detect static strain, but the detection circuit is complicated. Each has the characteristics that it can be detected and the detection circuit is simple, but the sensitivity is low.

[0003]

In the conventional sensor in which the strain resistance element is provided on the beam, in order to improve the detection sensitivity, the resistor of the external circuit, or the resistor and the strain resistance provided on the fixing portion of the beam are used. A Wheatstone bridge was constructed with the elements, and a signal amplification circuit was incorporated in the fixed part of the beam.

However, the above-mentioned structure has the problems that the characteristics of the sensor vary and the manufacturing cost increases, and a sensor having higher detection sensitivity is demanded.

Therefore, an object of the present invention is to solve the above problems, and to provide a small-sized, lightweight, high-performance displacement sensor having high detection sensitivity, and an acoustic / ultrasonic sensor, an acceleration sensor, an angular velocity sensor, and the like using the displacement sensor. To do.

[0006]

In order to achieve the above object, the displacement sensor of the present invention comprises both cantilever beams and a strain resistance element provided on one surface of each of the both moist beams. At least two are provided in the vicinity of the fixed portions of both the domed beams, at least two are provided at the center of the domed beams, and a Wheatstone bridge circuit is formed by the at least four strain resistance elements. . Alternatively, it is characterized in that the displacement sensor is an array displacement sensor in which a plurality of one-dimensionally or two-dimensionally produced on the same substrate.

In the above construction, it is preferable that the resistance values of the strain resistance elements provided on one surface of the two dovetail beams when they are not strained are substantially the same.

Next, the sound wave / ultrasonic sensor of the present invention uses the displacement sensor of the present invention or the array displacement sensor described above to measure the size of the flexure of the two beam beams of the sensor, or the size of the flexure and the respective phases. By detecting
It is characterized in that the magnitude of vibration of gas or liquid, or the magnitude of vibration and the propagation direction of vibration is measured.

Next, the acceleration sensor of the present invention is characterized in that the displacement sensor of the present invention is attached to an object to be measured to detect vibration, impact or acceleration applied to the object to be measured.

Next, in the angular velocity sensor of the present invention, the array displacement sensor of the present invention is attached to the object to be measured, and the magnitude and direction of the deflection of both the mochi beams of the plurality of sensors are detected to measure the object to be measured. It is characterized by detecting an angular velocity applied to an object.

Further, in the acceleration or angular velocity sensor of the above invention, it is preferable that the displacement sensor is housed in a container and the container is depressurized or filled with helium gas.

Further, in the various sensors of the above invention,
The strain resistance element is preferably made of at least one selected from semiconductor diffused resistors, thin film metal resistors, and thin film semiconductor resistors.

Further, in the various sensors of the above invention,
It is particularly preferable that the strain resistance element is composed of a resistor in which fine metal particles are dispersed in an insulator.

[0014]

According to the structure of the displacement sensor of the present invention, when an external force is applied to both the domed beams, the beams are deformed into an arc shape, and the strain resistance elements provided on one surface are provided at the central portion. The resistance value of the strain resistance element and the resistance value of the strain resistance element provided near the fixed part have different directions of change, and when one increases, the other decreases, and when one decreases, the other increases. .
Therefore, by arranging these strain resistance elements on the surface to form a Wheatstone bridge, it is possible to measure the displacement of both cantilever beams, that is, the applied external force with high sensitivity.

Further, the sensitivity can be maximized by forming the strain resistance elements provided on one surface of the two dovetail beams so that the resistance values thereof are substantially the same when no strain occurs.

Further, by using the displacement sensor of the present invention, it is possible to measure sound waves, ultrasonic waves and accelerations with high sensitivity with a simple structure, and it is possible to form an inexpensive, highly reliable and highly sensitive sensor.

Further, since the displacement sensor of the present invention has a simple monolithic structure, it is possible to easily fabricate a plurality of displacement sensors one-dimensionally or two-dimensionally on the same substrate by using a semiconductor process. By using such an array displacement sensor, it is possible to detect the magnitude and phase of displacement of a plurality of both cantilever beams with high accuracy with little variation in response speed, and to measure the propagation direction and angular velocity of sound waves and ultrasonic waves.

Further, in an acceleration sensor or an angular velocity sensor in which the displacement sensor is housed in a container and the inside of the container is in a decompressed state or filled with helium gas, there is no influence of wind or air fluctuations around the sensor. Accurately measure acceleration and angular velocity.

Further, a semiconductor diffused resistor as a strain resistance element,
By using at least one selected from thin-film metal resistors or thin-film semiconductor resistors, a semiconductor process can be utilized, reproducibility is good, and mass production is possible at low cost.
In particular, a strain resistance element composed of a resistor in which fine metal particles are dispersed in an insulator is easy to manufacture, has a large strain-resistance change rate, and is extremely effective as a strain resistance element for a displacement sensor.

[0020]

【Example】

(Embodiment 1) FIG. 1 is a perspective view of a displacement sensor according to a first embodiment of the present invention, and FIG. 2 is an equivalent circuit of the displacement sensor shown in FIG. In FIG. 1, a recess 11 is formed in a silicon substrate 1, and a doubly supported beam 10 made of an electrically insulating thin film 2 is formed thereon. There are four strain resistance elements 3a, 3
b, 4a, 4b, input terminals 5, 6, output terminals 7, 8 and wiring 9 are formed.

The above displacement sensor is manufactured as follows. First, a silicon oxide thin film 2 having a thickness of 1 μm is formed on a Si (100) substrate by a thermal oxidation process, and an Au / Cr thin film (Cr; 0.05 μm) having a thickness of 0.2 μm is formed on the silicon oxide thin film 2. Then, the wiring pattern 9 and the input / output terminals 5, 6, 7, and 8 are formed by the photolithography method. Next, with respect to the substrate on which the wiring pattern 9 and the input / output terminals 5, 6, 7 and 8 are formed, a 0.3 μm thick nickel-chromium alloy thin film (C
r; 20 at%) is formed by the sputtering method, and the pattern 12 as shown in FIG. 3 is formed by the photolithography method.
The strain resistance elements 3a, 3b, 4a, and 4b having The strain resistance elements 3a, 3b, 4a, 4b form a Wheatstone bridge. Further, by etching the silicon oxide thin film 2 with diluted hydrogen fluoride water by a photolithography method, a length of 2 mm and a width of 0.
A 4 mm double-bearing beam 10 is formed, and subsequently, the silicon substrate 1 is anisotropically etched with potassium hydroxide to form a concave portion 11 to complete the displacement sensor.

In order to investigate the characteristics of the displacement sensor formed as described above, a DC voltage of 2V was applied between the input terminals 5 and 6, and the voltage between the output terminals 7 and 8 was measured.
A stable output of 4 mV was obtained for a strain of%. Also,
It was proved that the displacement sensor had an excellent temperature characteristic of 20 ppm / ° C or less. Furthermore, by incorporating the amplifier circuit in the silicon substrate, the sensitivity could be further improved without degrading the S / N.

Since each strain resistance element is formed by a thin film process and a photolithography process, the variation in its resistance value is small, and a resistance value of 1% or less can be easily formed. Therefore, the output voltage without distortion is small, amplification is easy, and sensitivity is high.

Further, since the above displacement sensor has low noise and high sensitivity, it can easily detect a weak sound wave or ultrasonic wave propagating in air or liquid, and by fixing this displacement sensor to the object to be measured. Also, vibration and acceleration applied to the object to be measured can be measured with high sensitivity.

(Second Embodiment) A displacement sensor according to a second embodiment of the present invention in which the displacement sensors are arranged in an array will be described below with reference to the drawings.

FIG. 4 is a perspective view showing a structure of a one-dimensional array displacement sensor in which a plurality of both cantilever beams 10 are formed on the same silicon substrate 1. This array sensor can also be formed by the same semiconductor process as the above displacement sensor.

By using the above array sensor to emit a pulsed sound wave or ultrasonic wave toward an object and detecting a reflected wave from the object with this array sensor, the shape, property, and object of the object can be obtained. I was able to measure the distance and direction to an object.

Specifically, when the magnitude of output voltage of each sensor, the phase difference, and the time from emission to detection are measured and processed, firstly, from the magnitude of the output voltage, the property of the object is determined. It was possible to measure the direction and shape of the target object from the phase difference 2 and the distance to the target object 3 from the time from the emission to the detection. In addition, in the case of the one-dimensional array sensor, only in-plane information can be obtained, but it goes without saying that three-dimensional information can be obtained by using the two-dimensional array sensor. The displacement sensor described above is not only useful as an image sensor for an object in the air or in a liquid, but also extremely useful as a diagnostic device for imaging the state inside the body with high resolution.

(Third Embodiment) A third embodiment of the present invention in which the above displacement sensor is applied to an angular velocity sensor will be described below with reference to the drawings.

FIG. 5 is a perspective view showing the structure of an angular velocity sensor according to the third embodiment of the present invention. This sensor is composed of two displacement sensors 13 and 14 formed on the same substrate, and measures the angular velocity by processing the output from the two sensors generated when rotation is applied about the axis 15 as a central axis. Is.

When the displacement sensor of the present invention is used as an acceleration sensor or an angular velocity sensor, by accommodating the sensor itself in a hermetically sealed container, noise due to air flow and fluctuation is eliminated, and stable output with high S / N is obtained. Further, sensitivity and temperature characteristics can be improved by reducing the pressure in the container to several mmHg or less or by filling with helium gas. It is considered that this is because the air resistance received by both mochi beams has decreased.

In the above embodiment, a metal thin film resistor made of nickel-chromium alloy was used as the strain resistance element. However, a thin film resistor in which fine metal particles are dispersed in an insulator, or a semiconductor such as silicon or gallium arsenide is doped with impurities. Semiconductor diffused resistors or thin film semiconductor resistors such as germanium or amorphous silicon can also be used.

When the above semiconductor diffusion resistance is used, both strain beams are made of the same semiconductor material, and the surface thereof is doped with an impurity, so that the strain resistance element can be easily formed on the surface of both strain beams. However, it has the advantage of high sensitivity, but has the disadvantage of poor temperature characteristics. On the other hand, thin-film metal resistors have excellent temperature characteristics but low sensitivity, and semiconductor thin-film resistors show intermediate characteristics between semiconductor diffused resistors and thin-film metal resistors.

However, as a whole, a thin film resistor in which fine metal particles are dispersed in an insulator has excellent temperature characteristics and sensitivity, is easy to prepare, and can produce a sensor having excellent stability with good reproducibility. The thin film resistor in which fine metal particles are dispersed in this insulator can be formed by alternately sputtering gold and silicon oxide at least once, for example, to form a thin film resistor made of silicon oxide in which fine gold particles are dispersed. As the metal fine particles, noble metals such as gold, platinum, silver, and copper were chemically stable and exhibited particularly excellent characteristics. As the insulator, in addition to silicon oxide, aluminum oxide, aluminum nitride, titanium oxide, rare earth oxide, etc. showed excellent characteristics.

Although the case where a silicon oxide thin film is used as the both-supported beam has been shown, in addition to this, a silicon doubly-supported beam or a silicon nitride thin-film doubly-supported beam produced from a silicon wafer by a micromachining technique is also used. be able to. The above-mentioned silicon dovetail beam has the advantage that a strain resistance element can be integrally formed by ion-implanting boron or the like on the surface. It has a great advantage that it can be formed by a silicon integrated circuit process, and the silicon nitride bilateral dovetail beam has a large fracture strength and can produce a sensor excellent in impact resistance.

[0036]

As described above, it is composed of both cantilever beams and a strain resistance element provided on one surface of both cantilever beams, and at least two strain resistance elements are provided in the vicinity of the fixed portions of both cantilever beams. At least two in the center of the mochi beam, at least four
According to the configuration of the present invention in which the Wheatstone bridge circuit is formed by the individual strain resistance elements, the semiconductor process technology capable of high-precision processing can be used, and the strain resistance material having a small strain-resistance coefficient is used. In addition, it is possible to mass-produce high-sensitivity and small displacement sensors, acoustic / ultrasonic sensors, acceleration sensors, angular velocity sensors, array sensors, etc. at low cost.

Further, since both cantilever beams can be manufactured by using a semiconductor substrate made of silicon or the like, a circuit for amplifying and detecting a minute change in resistance value of the strain resistance element and a signal processed by a plurality of sensors are arithmetically processed, It is possible to build a circuit to be imaged in the substrate, and in particular, in an imaging sensor, further miniaturization, weight reduction, and higher performance are possible.

[Brief description of drawings]

FIG. 1 is a perspective view of a displacement sensor according to an embodiment of the present invention.

FIG. 2 is a diagram showing an equivalent circuit of a displacement sensor according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a strain resistance element used in a displacement sensor according to an embodiment of the present invention.

FIG. 4 is a perspective view of an array displacement sensor according to an embodiment of the present invention.

FIG. 5 is a perspective view of an angular velocity sensor according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Electrically insulating thin film 3a, 3b, 4a, 4b Strain resistance element 5, 6 Input terminal 7, 8 Output terminal 10 Both stick beams 11 Recess 12 Metal thin film 13, 14 Displacement sensor 15 Rotation axis

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takao Nita 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (9)

[Claims] 1. A displacement sensor comprising: a substrate having irregularities; both cantilever beams fixed to the convex portions of the substrate; and a strain resistance element formed on a main surface of the both cantilever beams, the strain sensor comprising: The resistance element includes a plurality of first strain resistance elements formed in the vicinity of the fixed portions of the both moist beams to the substrate and a plurality of second strain elements formed on the concave portions of the both moist beams in the substrate. A displacement sensor having a resistance element, wherein a Wheatstone bridge circuit is formed by the first strain resistance element and the second strain resistance element. 2. A substrate having irregularities, a plurality of both-bearing beams fixed to the protruding portions of the substrate and formed in an array, and a strain resistance element formed on a main surface of the both-bearing beams. In the displacement sensor, the strain resistance elements are formed on a plurality of first strain resistance elements formed in the vicinity of the fixing portions of the both moist beams to the substrate and on the concave portions of the both moist beams of the substrate. A displacement sensor having a plurality of second strain resistance elements, wherein a Wheatstone bridge circuit is formed by the first strain resistance element and the second strain resistance element. 3. A displacement sensor comprising: a substrate having irregularities; both cantilever beams fixed to the convex portions of the substrate; and a strain resistance element formed on a main surface of the both cantilever beams, the strain sensor comprising: The resistance element includes a plurality of first strain resistance elements formed in the vicinity of the fixed portions of the both moist beams to the substrate and a plurality of second strain elements formed on the concave portions of the both moist beams in the substrate. A substrate having a resistance element, wherein a Wheatstone bridge circuit is formed by the first strain resistance element and the second strain resistance element, and further, both mochi beams fixed with the strain resistance element are fixed; A displacement sensor characterized by being housed in a depressurized state or in a container filled with helium gas. 4. The displacement sensor according to claim 1, wherein the strain resistance element is made of at least one selected from semiconductor diffusion resistance, thin film metal resistance and thin film semiconductor resistance. 5. The displacement sensor according to claim 1, wherein the strain resistance element is composed of a resistor in which fine metal particles are dispersed in an insulator. 6. A displacement sensor comprising: a substrate having irregularities; both cantilever beams fixed to the convex portions of the substrate; and a strain resistance element formed on a main surface of both of the cantilever beams. The resistance element includes a plurality of first strain resistance elements formed in the vicinity of the fixed portions of the both moist beams to the substrate and a plurality of second strain elements formed on the concave portions of the both moist beams in the substrate. A displacement measuring method using a displacement sensor having a resistance element, wherein a Wheatstone bridge circuit is formed by the first strain resistance element and the second strain resistance element, the deflection measuring method comprising: Displacement measuring method characterized by measuring the vibration displacement of gas or liquid by detecting the vibration. 7. A substrate having irregularities, a plurality of both-bearing beams fixed to the protruding portions of the substrate and formed in an array, and a strain resistance element formed on a main surface of the both-bearing beams. In the displacement sensor, the strain resistance elements are formed on a plurality of first strain resistance elements formed in the vicinity of the fixing portions of the both moist beams to the substrate and on the concave portions of the both moist beams of the substrate. A displacement measuring method using a displacement sensor having a plurality of second strain resistance elements, wherein a Wheatstone bridge circuit is formed by the first strain resistance element and the second strain resistance element. A displacement measuring method, characterized in that the magnitude of vibration of a gas or a liquid and the propagation direction of the vibration are measured by detecting the magnitudes of the deflections of the plurality of both cantilevers and the respective phases. 8. A displacement sensor comprising: a substrate having irregularities; both cantilever beams fixed to the convex portions of the substrate; and a strain resistance element formed on a main surface of the both cantilever beams, wherein the strain sensor comprises: The resistance element includes a plurality of first strain resistance elements formed in the vicinity of the fixed portions of the both moist beams to the substrate and a plurality of second strain elements formed on the concave portions of the both moist beams in the substrate. A displacement measuring method using a displacement sensor having a resistance element, wherein a Wheatstone bridge circuit is formed by the first strain resistance element and the second strain resistance element, wherein the displacement sensor is used as an object to be measured. A displacement measuring method, which comprises mounting and measuring displacement of vibration or acceleration applied to an object to be measured. 9. A substrate having irregularities, a plurality of both-bearing beams fixed to the protruding portions of the substrate and formed in an array, and a strain resistance element formed on a main surface of the both-bearing beams. In the displacement sensor, the strain resistance elements are formed on a plurality of first strain resistance elements formed in the vicinity of the fixing portions of the both moist beams to the substrate and on the concave portions of the both moist beams of the substrate. A displacement measuring method using a displacement sensor having a plurality of second strain resistance elements, wherein a Wheatstone bridge circuit is formed by the first strain resistance element and the second strain resistance element. A displacement measuring method characterized in that the displacement sensor is attached to an object to be measured, and the angular velocity applied to the object to be measured is detected by detecting the sizes and directions of the deflections of the plurality of both cantilever beams.