JP2002040045A - Dynamic quantity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the resonance of a bar-like movable electrode and fixed electrode in detection to improve the precision of sensor output in a dynamic quantity sensor for detecting an applied dynamic quantity on the basis of the change in space between the movable electrode and fixed electrode in the application of the dynamic quantity while giving a periodically changing carrier wave signal to the movable and fixed electrodes. SOLUTION: The individual movable electrode 24 has a bar-like shape extending protrusively from a weight part 21 supported displaceably in Y-axial direction to a first silicon base 11, and the individual fixed electrode 31, 32 has a bar-like shape cantilever-supported by the first silicon base 11 and having a side surface extending protrusively so as to be opposite to the side surface of the movable electrode 24, wherein 1/an integer times the natural frequency in the bending and vibration of the movable electrode 24 and the fixed electrodes 31 and 32 is out of the frequency of a carrier wave signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a rod-shaped movable electrode supported so as to be displaceable in a predetermined direction with respect to a base, and a rod-shaped fixed electrode fixed to the base so as to face the movable electrode. The present invention relates to a dynamic quantity sensor that detects a applied physical quantity based on a change in an interval between a movable electrode and a fixed electrode when a dynamic quantity is applied while giving a periodically changing carrier signal to the movable and fixed electrodes.

[0002]

2. Description of the Related Art Conventionally, as a dynamic quantity sensor of this kind, for example, a semiconductor dynamic quantity sensor described in Japanese Patent Application Laid-Open No. H11-326365 has been proposed. FIG. 8 shows a general schematic plan configuration of such a sensor. By forming a groove 14 by etching or the like in the semiconductor layer 12 supported on the support substrate 11 as a base on which the opening 13a is formed, the movable portion 920 and the movable portion 92 are formed.
The fixing portion 930 is formed so as to be separated from the support substrate 11 by a groove 14 and the groove 14.

Here, the movable portion 920 includes a weight portion 921 which can be displaced in the Y-axis direction (predetermined direction Y) indicated by a double-headed arrow in FIG. Part 9
And a rod-shaped movable electrode 924 formed on both left and right sides of the movable electrode 21.
24 fixed electrode 93 arranged to face the side surface
1, 932.

A movable electrode 9 is applied in response to the application of a mechanical quantity.
Since the distance between the movable electrode 924 and the fixed electrodes 931 and 932 (the detection interval 940 in FIG. 8) changes when the H. 24 is displaced in the Y-axis direction, the applied dynamic quantity is determined based on the change in the detection interval 940. Is detected.

Generally, a change in the detection interval 940 is detected as a change in capacitance between the movable and fixed electrodes. The capacitance (first capacitance) between the first fixed electrode 931 and the movable electrode 924 is CS1, and the second fixed electrode 932 and the movable electrode 924 are
Assuming that the capacitance (second capacitance) between the two is CS2, a detection circuit diagram of this physical quantity sensor is shown in FIG.

Here, 25a is a movable electrode pad, 31b
And 32b are fixed electrode pads, which correspond to the pads shown in FIG. 8, respectively. Reference numeral 81 denotes a switched capacitor circuit (SC circuit).
A capacitor 82 having a capacitance of Cf, a switch 83, and a differential amplifier circuit 84 are provided.
S2) is converted into a voltage.

FIG. 4 shows an example of a timing chart for the circuit shown in FIG. In the above physical quantity sensor, for example, the carrier wave 1 (for example, a frequency of 100 kHz, the amplitude is 0 to 5 V) from the fixed electrode pad 31b, and the carrier wave 2 which is 180 ° out of phase with the carrier wave 1 from the fixed electrode pad 32b.
(For example, a frequency of 100 kHz and an amplitude of 5 to 0 V), and the switch 83 of the SC circuit 81 is opened and closed at the timing shown in the figure. Then, the applied mechanical quantity is output as a voltage value V0 as shown in the following Expression 1.

[0008]

V0 = (CS1-CS2) .V / Cf Here, V is a voltage difference between both pads 31b and 32b. As shown in the timing chart, in a conventional physical quantity sensor, it is general that the detection of the physical quantity is detected in accordance with the period of the carrier signal that changes periodically.

[0009]

However, in the above-described conventional physical quantity sensor, since the movable electrode 924 and the fixed electrodes 931 and 932 are rod-shaped, the carrier signal (carrier waves 1 and 2) applied for detection is not detected. When the frequency matches the natural frequency of these electrodes, these electrodes 92
4, 931 and 932 resonate and bend and vibrate in a direction intersecting the longitudinal direction of the rod.

Then, the interval between the movable and fixed electrodes changes, and in addition to the change in the detection interval 940 due to the application of a regular physical quantity, the above-mentioned detection interval 940 is caused by the resonance of this electrode.
Changes, an error occurs in the sensor output, causing a problem.

In view of the above problems, the present invention provides a periodically movable carrier signal to a rod-shaped movable and fixed electrode and, when a mechanical quantity is applied, sets a distance between the movable electrode and the fixed electrode. In a physical quantity sensor that detects an applied physical quantity based on a change, an object of the present invention is to suppress resonance of a movable electrode and a fixed electrode at the time of detection and improve the accuracy of a sensor output.

[0012]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a base (11) and a rod-shaped movable electrode supported to be displaceable in a predetermined direction (Y) with respect to the base. (24) and a rod-shaped fixed electrode (31, 32) supported on the base so as to face the movable electrode, and while applying a periodically changing carrier signal to the movable electrode and the fixed electrode, When an amount is applied, in a dynamic quantity sensor that detects an applied dynamic quantity based on a change in the distance between the movable electrode and the fixed electrode, 1 / integer of the natural frequency when the movable electrode and the fixed electrode perform bending vibration. The double is deviated from the frequency of the carrier signal.

According to the present invention, the frequency of the carrier signal is 1 / integer times the natural frequency at which the rod-shaped movable electrode and the fixed electrode vibrate flexibly. Can be suppressed, and the accuracy of the sensor output can be improved. It should be noted that the natural frequency of 1
/ Integer multiple means that it is actually impossible to be negative or 0, so that it is 1 ×, 1/2 ×, 1/3 ×, that is, 1 / n
Means that n is a positive integer.

Here, 1 / integer multiple of the natural frequency when the movable electrode (24) and the fixed electrode (31, 32) bend and vibrate as in the second aspect of the present invention is ±± from the frequency of the carrier signal. It is preferable that the deviation is 5% or more. This is because the variation in the frequency of the carrier signal occurs up to about ± 5% in consideration of the variation in the circuit that generates the carrier signal.

Further, the invention according to claim 3 is characterized in that 1 / integer multiple of the natural frequency is 1 or 1/2. That is, it is preferable that the frequency of the carrier signal deviates from an integral multiple of 2 or less of the natural frequency when the movable electrode and the fixed electrode perform bending vibration. This is because when the frequency of the carrier signal is less than twice the natural frequency, the electrode tends to resonate, but when the frequency is three times or more, the bending vibration of the rod-shaped electrode is difficult to follow, that is, the resonance is difficult. Therefore, the influence on the sensor output is reduced.

Further, the invention of claim 4 provides a specific configuration of a movable and fixed electrode, wherein the movable electrode (24) is provided.
Is provided on a weight portion (21) supported to be displaceable in a predetermined direction (Y) with respect to the base portion (11), and the weight portion is located at a base in a direction orthogonal to the predetermined direction. Fixed electrodes (31, 32), protruding rods
Is characterized in that it has a rod-like shape protruding from the base side as a root.

According to a fifth aspect of the present invention, in the electrode configuration of the fourth aspect, the movable electrode (24) and the fixed electrode (3) are provided.
1, 32) is characterized in that the base side has a wide shape so as to increase rigidity as compared with the front end side in the protruding direction.

According to this, the roots of the movable and fixed electrodes are formed wider than the distal end in the protruding direction, and the rigidity is increased. As a result, the natural vibration of the bending vibration of the movable and fixed electrodes is obtained. Since the number can be increased, 1 / integer multiple of the natural frequency can be appropriately excluded from the frequency of the carrier signal.

Further, in the movable electrode (24) and the fixed electrodes (31, 32), portions other than the portion located at the interval (40) for detecting the applied dynamic quantity are projected. By doing so, it is preferable to have the above-mentioned wide shape.

This is because the movable and fixed electrodes have a wide shape by protruding a portion other than the portion located at the distance for detecting the physical quantity, so that the detection interval (40) between both electrodes can be widened without changing. This is because the shape can be realized.

According to a seventh aspect of the present invention, in the electrode structure of the fourth aspect, the movable electrode (24) and the fixed electrode (3) are provided.
1, 32) are formed in a rigid frame structure shape in which a plurality of rectangular frame portions (55) are connected, and the size of the rectangular frame portion is the tip of the movable electrode and the fixed electrode in the projecting direction. It is characterized in that it becomes smaller as going from the side to the root side.

According to this, since the rigidity of the base portion side of the movable and fixed electrodes can be made larger than that of the tip end portion in the protruding direction, the same operation and effect as the invention of claim 5 can be exhibited. it can.

In the invention according to claim 8, the base (11)
A weight portion (21) supported to be displaceable in a predetermined direction (Y) with respect to the base portion; and a rod-shaped member formed integrally with the weight portion and extending from the weight portion and protruding in a direction orthogonal to the predetermined direction. A movable electrode (24), a rod-shaped fixed electrode (31, 32) protruding from the base so as to face the movable electrode, and a periodically changing carrier signal applied to the movable electrode and the fixed electrode. In the physical quantity sensor that detects the applied physical quantity based on a change in the distance between the movable electrode and the fixed electrode when the quantity is applied, both the movable electrode and the fixed electrode have the base side in the protruding direction and the protruding direction in the protruding direction. It is characterized by having a higher rigidity than the distal end side.

According to the present invention, the strength of the movable electrode and the fixed electrode can be improved. And, for example, for the purpose of suppressing the resonance of the movable and fixed electrodes at the time of detection,
Since the base side in the protruding direction of each electrode has higher rigidity than the tip side in the protruding direction, the natural frequency can be easily increased as compared with the frequency of the carrier signal. The same effect as the first aspect can be obtained.

The reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention shown in the drawings will be described below. In the first embodiment, the physical quantity sensor of the present invention is, for example, an airbag,
A description will be given assuming that the present invention is applied to a differential capacitance type semiconductor acceleration sensor that can be applied to an acceleration sensor for a vehicle, a gyro sensor, or the like for performing operation control of a BS, a VSC, or the like.

FIG. 1 shows a schematic plan configuration of a semiconductor acceleration sensor (hereinafter simply referred to as a sensor) 100, and FIG.
A schematic cross-sectional structure along the line AA in FIG. In addition,
In FIG. 1, the same parts as those in FIG. 8 described in the section of "Prior Art" are denoted by the same reference numerals.

The semiconductor acceleration sensor 100 is formed by subjecting a semiconductor substrate to micromachining using a known semiconductor manufacturing technique. As shown in FIG. 2, the semiconductor substrate constituting the sensor 100 includes a first silicon substrate (a base in the present invention) 11 as a first semiconductor layer and a second silicon substrate 12 as a second semiconductor layer. A rectangular SOI substrate 10 having an oxide film 13 as an insulating layer between them.

By forming the groove 14 in the second silicon substrate 12, a beam structure including the movable part 20 and the fixed part 30 partitioned by the movable part 20 and the groove 14 is formed. I have. Further, portions of the oxide film 13 and the first silicon substrate 11 corresponding to the regions where the beam structures 20 and 30 are formed are removed in a rectangular shape by sacrificial layer etching or the like to form openings 13a. And the fixing part 3
Reference numeral 0 denotes an opening edge of the opening 13a, which is supported by the first silicon substrate 11 via the oxide film 13.

The movable part 20 arranged so as to cross over the opening 13a is formed by connecting both ends of a rectangular weight 21 to a beam 22.
And are integrally connected to the anchor portions 23a and 23b via the. These anchor portions 23a and 23b
Is fixed to the opening edge of the opening 13 a in the oxide film 13 and is supported on the first silicon substrate 11. As a result, the weight 21 and the beam 22 face the opening 13a.

The beam portion 22 has a rectangular frame shape in which two beams are connected at both ends thereof, and has a spring function of displacing in a direction orthogonal to the longitudinal direction of the beam. Specifically, when receiving an acceleration including a component in the Y-axis direction indicated by an arrow Y in FIG. 1, the beam portion 22 displaces the weight portion 21 in the Y-axis direction, and responds to the disappearance of the acceleration. The original state is restored.

As described above, the weight portion 21 is supported so as to be displaceable in the Y-axis direction (predetermined direction Y) with respect to the first silicon substrate 11, and the weight portion 21 is placed on the opening 13a in response to the application of acceleration. It is adapted to be displaced in the Y-axis direction.

A plurality (6 in the illustrated example) is provided on both side surfaces (left and right sides in FIG. 1) of the weight portion 21 about the axis of the weight portion 21 along the Y-axis direction. The rod-shaped movable electrode 24) protrudes and extends in a direction orthogonal to the Y-axis, and is formed in a comb shape. Each movable electrode 24 is formed in the shape of a beam having a rectangular cross section, and the opening 13 is formed.
a. As described above, the movable electrode 24 integrally formed with the weight 21 can be displaced in the Y-axis direction together with the weight 21.

Further, the fixed portion 30 is provided for each movable electrode 24.
There are provided a plurality of rod-shaped fixed electrodes 31 and 32 protruding from the first silicon substrate (base) 11 so as to face the same. Each of the fixed electrodes 31 and 32 is connected to the first silicon substrate 1.
1 and are opposed to each other so as to mesh with the gaps between the comb teeth of the pair of left and right comb-shaped movable electrodes 24 of the weight portion 21.

The pair of left and right fixed electrodes 31 and 32 are composed of a first fixed electrode 31 located on the left side in FIG. 1 and a second fixed electrode 32 located on the right side. And the second fixed electrode 32 are electrically independent of each other. Individual fixed electrodes (6 on each side in the illustrated example) 3
Reference numerals 1 and 32 are formed in a beam shape having a rectangular cross section, and are in a state facing the opening 13a while being supported in a cantilever manner by the respective wiring portions 31a and 32a.

The side surface of each of the fixed electrodes 31 and 32 is opposed to the side surface of each of the movable electrodes 24 in parallel with a predetermined interval. Here, the smaller one of the opposing intervals of the movable and fixed electrodes 24, 31, and 32 is the detection interval 40 used for detecting a change in capacitance during acceleration detection, and is the opposite side to the detection interval 40. The larger interval is a non-detection interval that is not used for detecting a change in capacitance when detecting acceleration.

Here, in the first embodiment, FIG.
As shown in the figure, each movable electrode 24 and fixed electrodes 31, 3
In 2, the wide portions 26 and 36 are provided on the base portion side in the protruding direction to increase the rigidity on the base portion side as compared with the distal end portion in the protruding direction.

Each wiring portion 3 of each fixed electrode 31, 32
Fixed electrode pads 31b and 32b for wire bonding are formed at predetermined positions on 1a and 32a, respectively. A movable electrode wiring portion 25 is formed integrally with one anchor portion 23b, and a movable electrode pad 25a for wire bonding is formed at a predetermined position on the wiring portion 25. ing. Each of the electrode pads 25a, 31b, 32b is formed of, for example, aluminum.

Further, the weight portion 21 is formed with a plurality of rectangular through-holes 50 penetrating from the opening 13a side to the opposite side. A structural shape is formed. Thereby, the weight of the movable section 20 is reduced and the torsional strength is improved.

Further, as shown in FIG.
A package 70 on the back surface (the surface opposite to the oxide film 13) of the first silicon substrate 11 via the adhesive 60.
Adhesively fixed. The package 70 contains circuit means 80 described later. Then, this circuit means 80 and each of the above-mentioned electrode pads 25a, 31b, 32b
Are electrically connected by a wire (not shown) formed by gold or aluminum wire bonding or the like.

In such a configuration, the first capacitor (CS1), the second fixed electrode 32 and the movable electrode 24 are provided at the detection interval 40 between the first fixed electrode 31 and the movable electrode 24.
A second capacitor (referred to as CS2) is formed at the detection interval 40 between the first and second capacitors. When the acceleration is received, the entire movable portion 20 is integrally displaced in the Y-axis direction by the spring function of the beam portion 22, and each of the capacitors CS 1,
CS2 changes. The detection circuit 80 detects the differential capacitance (CS1) between the movable electrode 24 and the fixed electrodes 31 and 32.
-Acceleration is detected based on the change of CS2).

FIG. 3 shows a detection circuit diagram of the present sensor 100. In the detection circuit 80, reference numeral 81 denotes a switched capacitor circuit (SC circuit). The SC circuit 81 includes a capacitor 82 having a capacitance of Cf, a switch 83, and a differential amplifier circuit 84. −CS
2) is converted into a voltage.

FIG. 4 shows an example of a timing chart for the detection circuit 80. In the sensor 100, for example, the carrier 1
(For example, frequency 100 kHz, amplitude 0 to 5 V), carrier 2 (for example, frequency 100 kHz, amplitude 5 to 0) having a phase shifted from carrier 1 by 180 ° from fixed electrode pad 32b.
V), the switch 83 of the SC circuit 81 is opened and closed at the timing shown in the figure. Then, the applied acceleration is output as a voltage value V0, as shown in the above-described Expression 1.

As described above, the present sensor 100 applies a periodically changing carrier wave signal (carrier wave 1 and carrier wave 2) to the movable electrode 24 and the fixed electrodes 31 and 32 while applying acceleration. Side surface of movable electrode 24 and fixed electrode 3
The applied acceleration is detected based on a change in the detection interval 40 between the side surfaces 1 and 32.

In this sensor 100, since the movable electrode 24 and the fixed electrodes 31 and 32 are rod-shaped, if the frequency of the carrier signal applied for detection matches the natural frequency of these electrodes. , These electrodes 24,
31 and 32 resonate and bend and vibrate in a direction intersecting the longitudinal direction of the rod. Then, besides the change of the detection interval 40 due to the application of the regular acceleration, the resonance of the electrode causes the detection interval 4 to change.
Since 0 changes, an error occurs in the sensor output, causing a problem.

FIG. 5 is a diagram showing a result of examining the relationship between the frequency of the carrier signal (carrier frequency) and the output of the sensor (the voltage value V0). As shown in FIG. 5, when the carrier frequency coincides with 1 / integer multiple of the natural frequency (resonant frequency fe of the electrode) when the movable electrode 24 and the fixed electrodes 31 and 32 perform bending vibration, the output becomes constant. It can be seen that fluctuates greatly.

In order to avoid such a problem, in the present embodiment, 1 / integer times the natural frequency when the movable electrode 24 and the fixed electrodes 31 and 32 undergo bending vibration is excluded from the frequency of the carrier signal. The main feature is that. Specifically, as described above, the movable and fixed electrodes 24, 3
The root portion side in the protruding direction of the projections 1 and 32 has a wider shape than the tip side in the protruding direction, and by increasing the rigidity, as a result, the natural frequency of the bending vibration of the movable and fixed electrodes is increased, 1 / integer times the natural frequency of the electrode is excluded from the frequency of the carrier signal.

In the present sensor 100, for example, the frequency of the carrier signal is about 50 kHz to 150 kHz, and the frequency of the external acceleration (applied acceleration) is 0 to 5 kHz.
It is about 0 kHz. Therefore, if the natural frequency of the electrode is shifted from the carrier frequency to a lower side, the natural frequency of the electrode may overlap the frequency of the external acceleration, which is not preferable. Therefore, it is preferable to remove the natural frequency to a higher side than the carrier frequency.

Here, it is preferable that 1 / integer times of the natural frequency of the electrode deviate from the frequency of the carrier signal by ± 5% or more. This is because the variation in the frequency of the carrier signal is about ±
This is because it occurs up to about 5%.

Further, it is preferable that 1 / integer multiple of the natural frequency of this electrode is 1 or 1/2. this is,
When the frequency of the carrier signal is a high frequency of three times or more of the natural frequency, the bending vibration of the rod-shaped electrode becomes difficult to follow,
In other words, the resonance hardly occurs, so that the influence on the sensor output is reduced as shown in FIG.

(Second Embodiment) FIG. 6 shows a schematic plan configuration of a semiconductor acceleration sensor 200 according to a second embodiment of the present invention. This embodiment is obtained by modifying the shape of the rod-shaped movable and fixed electrodes 24, 31, and 32 in the first embodiment. Hereinafter, differences from the first embodiment will be mainly described. 6, the same reference numerals are given and the description is omitted.

In the sensor 200 shown in FIG. 6, similarly to the sensor 100 of the first embodiment, the rigidity of the base of the movable electrode 24 and the fixed electrodes 31 and 32 in the projecting direction is larger than that of the distal end. The shape is as wide as possible. Here, in the present embodiment, the movable electrode 24 and the fixed electrode 3
In 1 and 32, the above-mentioned wide shape is constituted by protruding the side surface opposite to the side surface located at the detection interval 40 for detecting the applied acceleration.

According to this, as in the first embodiment,
Since the base portions of the movable and fixed electrodes 24, 31, and 32 in the protruding direction have a wider shape than the tip portions and have higher rigidity, as a result, the natural frequency of the electrodes can be increased. In addition, 1 / integer times the natural frequency of the electrode can be appropriately excluded from the frequency of the carrier signal.

Further, as an effect peculiar to the second embodiment, in the movable and fixed electrodes 24, 31, and 32, the side surface opposite to the side surface located at the detection interval 40 is protruded, and the base portion side has a wide shape. By doing so, it is possible to easily achieve maintaining the detection interval 40 in a flat state.

Third Embodiment FIG. 7 shows a schematic plan configuration of a semiconductor acceleration sensor 300 according to a third embodiment of the present invention. This embodiment is obtained by modifying the shape of the rod-shaped movable and fixed electrodes 24, 31, and 32 in the first embodiment. Hereinafter, differences from the first embodiment will be mainly described. 6, the same reference numerals are given and the description is omitted.

In the sensor 300 shown in FIG.
4 and the fixed electrodes 31 and 32 are formed in a rigid frame structure shape in which a plurality of rectangular frame-shaped portions 55 are connected.
The size of the rectangular frame portion 55 decreases from the tip end side of the movable electrode 24 and the fixed electrodes 31 and 32 toward the base portion side.

In this embodiment, the movable and fixed electrodes 24 and the fixed electrodes 24 are formed by adopting such a rigid frame structure instead of the wide structure as in the first and second embodiments.
Since the base portion side of the protruding direction of 31 and 32 can have higher rigidity than the tip end side, the natural frequency of the electrode can be increased as a result, and the natural frequency of the electrode can be increased. Can be appropriately deviated from an integer multiple of the frequency of the carrier signal.

The sensor 1 according to each of the above embodiments is
In each of 00, 200, and 300, the root side of the movable electrode 24 and the fixed electrodes 31 and 32 in the protruding direction is
It has the feature that the rigidity is higher than that at the tip end side. And the sensor 100 having such characteristics
According to Nos. 300, there is an advantage that the natural frequency of the electrode can be easily increased as compared with the frequency of the carrier signal, and a 1 / integer multiple of the natural frequency can be excluded from the carrier frequency. In addition, there is an advantage that the strength and weight of the movable electrode and the fixed electrode can be improved.

It should be noted that the present invention applies a periodically changing carrier signal to the rod-shaped movable and fixed electrodes and, when a mechanical quantity is applied, sets the distance between the side surface of the movable electrode and the side surface of the fixed electrode. The present invention is applicable to a physical quantity sensor that detects an applied physical quantity based on a change, and is not limited to the above-described capacitive sensor.

The rod-shaped movable and fixed electrodes also include rod-shaped electrodes having a bent portion in the middle of the electrodes, and a detection interval is formed by opposing portions other than the side surfaces of both electrodes. Can be anything. Further, the present invention is applicable to various sensors other than an acceleration sensor, such as an angular velocity sensor and a pressure sensor, for detecting a physical quantity.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a semiconductor acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view taken along line AA in FIG.

FIG. 3 is a detection circuit diagram of the semiconductor acceleration sensor shown in FIG.

4 is a diagram showing an example of a timing chart for the detection circuit shown in FIG. 3;

FIG. 5 is a diagram illustrating a relationship between a frequency of a carrier signal and an output of a sensor.

FIG. 6 is a schematic plan view of a semiconductor acceleration sensor according to a second embodiment of the present invention.

FIG. 7 is a schematic plan view of a semiconductor acceleration sensor according to a third embodiment of the present invention.

FIG. 8 is a schematic plan view of a conventional general semiconductor dynamic quantity sensor.

[Explanation of symbols]

11: first silicon substrate (base), 21: weight, 24 ...
Movable electrode, 31: first fixed electrode, 32: second fixed electrode, 40: detection interval, 55: rectangular frame portion.

Claims (8)

[Claims] 1. A base (11), a rod-shaped movable electrode (24) supported to be displaceable in a predetermined direction (Y) with respect to the base, and supported by the base so as to face the movable electrode. Fixed electrodes (31, 32) in the form of rods, and when a mechanical quantity is applied while periodically changing a carrier signal to the movable electrode and the fixed electrode,
In a physical quantity sensor for detecting an applied physical quantity based on a change in an interval (40) between the movable electrode and the fixed electrode, 1 / integer multiple of a natural frequency when the movable electrode and the fixed electrode perform bending vibration. Is outside the frequency of the carrier signal. 2. The method according to claim 1, wherein a 1 / integer multiple of a natural frequency when the movable electrode (24) and the fixed electrode (31, 32) undergo bending vibration deviate from the frequency of the carrier signal by ± 5% or more. The physical quantity sensor according to claim 1, wherein: 3. The method according to claim 1, wherein the 1 / integer multiple of the natural frequency is 1 or 1/2.
The physical quantity sensor according to 1. 4. The movable electrode (24) is connected to the base (1).
1) is provided on a weight portion (21) supported to be displaceable in the predetermined direction (Y) with respect to 1), and protrudes from the weight portion side in a direction orthogonal to the predetermined direction and extends. The dynamic quantity according to any one of claims 1 to 3, wherein the fixed electrode (31, 32) has a rod shape, and the fixed electrode (31, 32) has a rod shape that protrudes from the base side. Sensor. 5. The movable electrode (24) and the fixed electrode (3).
5. The physical quantity sensor according to claim 4, wherein the root side of (1, 32) has a wide shape so as to increase rigidity as compared with the tip side in the protruding direction. 6. The movable electrode (24) and the fixed electrode (3).
6. The wide shape according to claim 5, wherein in (1, 32), a portion other than a portion located at an interval (40) for detecting the applied dynamic quantity is protruded to form the wide shape. Physical quantity sensor. 7. The movable electrode (24) and the fixed electrodes (31, 32) are formed in a rigid frame structure in which a plurality of rectangular frame portions (55) are connected. 5. The dynamic quantity sensor according to claim 4, wherein the distance from the tip of the movable electrode and the fixed electrode toward the root in the protruding direction decreases. 8. A base (11), a weight (21) supported to be displaceable in a predetermined direction (Y) with respect to the base, and formed integrally with the weight and from the weight in the predetermined direction. Rod-shaped movable electrode (24) protruding and extending in a direction orthogonal to
A rod-shaped fixed electrode (31, 32) protruding from the base so as to face the movable electrode; and providing a periodically changing carrier signal to the movable electrode and the fixed electrode, Is applied,
In a physical quantity sensor that detects an applied physical quantity based on a change in a distance between the movable electrode and the fixed electrode, the movable electrode and the fixed electrode both have a root portion in a protruding direction compared to a tip portion in a protruding direction. Physical quantity sensor characterized by high rigidity.