JPH01224628A - Vibration sensor structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the structure of a semiconductor type vibration sensor.

(Conventional technology) Traditionally, semiconductor sensors have been used to detect vibrations.

Detection of acceleration, etc. is performed.

For example, Japanese Utility Model Application Publication No. 61-102871 describes a method for detecting the deviation of a cantilever beam supported at one end.
A structure is shown in which weights are provided on both the upper and lower surfaces of the tip of the cantilever so that the entire center of gravity of the two weights coincides with the center in the thickness direction of the cantilever.

The one shown in Figure 3 is a vibration sensor that has already been put into practical use, and its overall size is about 1+nm.

FIG. 4 is a longitudinal sectional view thereof. In FIGS. 3 and 4, the semiconductor sensor is composed of a cantilever beam having an electrode d on the SL substrate, and the beam is made of SiO2. In this type of vibration input from the outside, a change in the capacitance C occurs due to a change in the distance between the cantilever beam and the substrate a, and the vibration is detected by detecting the amount of change. Several to dozens of cantilever beams are formed on the sensor.

Cantilever beam b□lb2 Tb3 Tb4・・・・・・
The vibration frequency varies depending on the length, and the vibration of the vibrating body is detected by the change in capacitance during vibration.

(Problems to be Solved by the Invention) However, in the above configuration, only vibrations at a specific frequency could be detected due to the restriction of the natural frequency of the cantilever beam. Therefore, many cantilevers had to be formed on the sensor so that it could detect a wider range of frequencies, which required the use of a large space.

In addition, although miniaturization and integration are important for vibration sensors, conventional ones cannot handle a wide range of vibration frequencies, making them undesirable as semiconductor sensors.

The sensor of the present invention aims to provide a vibration sensor that does not take up a large space and can detect vibrations over a wide range.

(Means for Solving the Problems) The present invention provides a semiconductor type sensor for detecting vibrations, which includes a substrate in which a recess is formed, a beam disposed on the recess and supported at both ends by the substrate, and a This vibration sensor structure includes a plurality of arm portions extending laterally from both sides, and causes a change in capacitance between the substrate and the arm portions.

(Function) When there is vibration input from the outside with the above configuration, the beam will swing uniformly if the vibration is low frequency, and the beam will swing uniformly as the vibration becomes high frequency.
A beam arranged on the substrate and a plurality of arms extending laterally from both sides of the beam form various natural vibration modes that form a mode having a tertiary node and resonate with the input vibration depending on the frequency of the vibration. is formed. At this time, changes in the capacitance of each arm are detected, and by combining these changes, the vibration frequency can be determined.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a recess 2 is formed in a Si substrate 1, a beam 3 is provided on the recess 2, and both ends of the beam 3 are connected to the Supported at both ends. The beam 3 has a plurality of arms 4.4 on both sides thereof.
... will be established. This beam is formed of an insulator such as SiO□ (silicon oxide), and metal wiring 5 of metal electrode 4a formed on the upper surface of each arm portion 4 is formed thereon. Normally, this beam 3 is formed by printing means or the like during the semiconductor manufacturing process. A recess 2 is formed in the space below the beam 3 by selective etching of silicon using acetic acid-nitric acid. The right side of the recess 2 in FIG. 1 is a signal processing circuit section 6 that calculates the voltage and current obtained from changes in capacitance formed between the beam 3 and the arm 4 and the recess 2. This method detects the vibration mode.

FIGS. 2(a), (b), (c), and (d) are diagrams showing the natural vibration modes of the above configuration. When vibration is input from the outside, depending on the frequency of the vibration, the Si substrate 1 (see FIG. 1) Various natural vibration modes that resonate with the input vibration are formed by the beam 3 disposed above and the plurality of arms 4 extending laterally from both sides of the beam 3. When the vibration is low frequency, the beam swings uniformly, and as the frequency increases, a mode with secondary and tertiary nodes is formed.The change in capacitance of each arm at this time is detected, and the combination of these is detected. This allows us to determine the frequency of vibration. For example, Fig. 2(a) shows an example corresponding to 5Hz, and in this mode, C□, C4°CG are large, and C,...
C,,C,is small. Figure 2 (b) corresponds to 7 KHz, and in this mode the beam itself vibrates greatly up and down, there is no phase difference on the beam side, and the central (:, , C4 is large,
C,, C, and Cs.

C6 has an intermediate size. The modes in FIG. 2(C) correspond to 10 KHz, have opposite phases, and C to C6 are all large. The mode in Fig. 2(d) is C,,
C, is large, C, C6 is small, and C, C4 remain unchanged.

These examples are modes determined based on experiments with one sensor, and modes such as those illustrated are established through vibration tests and put into practical use.

The present invention is completely different from the cantilever type shown in FIG. 3, and is operated by the achieved motion of the beam and the arms. Increasing the thickness of the beam increases the frequency, and making the arms longer corresponds to a lower vibration range, so it is desirable to set the beam and arms in accordance with the expected vibration.

In addition, the signal processing circuit section 6 detects the frequency of vibration caused by the change in capacitance due to the vertical movement of the electrode, and uses the detected value to operate a weight using vibration reduction means, such as an actuator with the opposite phase, to vibrate. It is possible to attenuate the

In addition to being effective as a vibration sensor, the present invention can also be used as an acceleration sensor, a collision sensor, or a raindrop sensor.

(Effects of the Invention) As described above, the present invention provides a semiconductor type sensor for detecting vibration, which includes a substrate in which a recess is formed, a beam disposed on the recess and supported at both ends by the substrate; Since the vibration sensor structure includes a plurality of arms extending laterally from both sides of the beam, and a change in capacitance occurs between the substrate and the arms, conventionally, as shown in FIG. In the structure shown, due to the restriction of the natural frequency of the cantilever beam, it is only possible to detect vibrations at a specific frequency.In order to detect a wider range of frequencies, multiple cantilevers must be mounted on the sensor. However, in the present invention, there is no need for this and many vibration modes can be detected despite the small size.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment for explaining the present invention in detail, FIGS. 2(a), (b), (c), and (d) are perspective views showing examples of types of vibration modes, The figure is a perspective view of a conventional example, and FIG. 4 is an enlarged sectional view of FIG. 3. 1...Si substrate, 2...concavity, 3...
... Beam, 4 ... Arm section, 5 ... Metal wiring, 6 ... Signal processing circuit section. Figure 1 Figure 2 r-1-1---- Figure 3 Figure %4

Claims (1)

[Claims] (1) A semiconductor type sensor that detects vibrations includes a substrate in which a recess is formed, a beam disposed on the recess and supported at both ends by the substrate, and a plurality of arms extending laterally from both sides of the beam. A vibration sensor structure in which capacitance changes occur between the substrate and the arm.