JP2003194845A - Semiconductor acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor acceleration sensor being adjustable in sensitivity to accelerations, while enhancing the accuracy of detecting accelerations by controlling the displacement of a weight part. <P>SOLUTION: The semiconductor acceleration sensor includes a support part 11 provided by etching a semiconductor substrate; the weight part 12 having moving electrodes 12a and 12b and displaced relative to the support part 11; a suspension part 13 protruding from the support part 11 to elastically support the weight part 12; a strain gauge resistance 14 whose resistance value is displaced according to the amount that the weight part 12 is displaced; and stoppers 15 and 16 controlling the maximum amount of displacement of the weight part 12 and having respective fixed electrodes 15a and 16a in positions opposite to the moving electrodes 12a and 12b. The sensor is provided with a displacement control circuit 2 for controlling the displacement of the weight part 12 by applying voltages between the moving electrodes 12a and 12b and the fixed electrodes 15a and 16a, and a computing circuit 3 for computing acceleration signals according to the output of the displacement control circuit 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor, and more particularly to a piezoresistive semiconductor acceleration sensor.

[0002]

2. Description of the Related Art As a semiconductor acceleration sensor used for detecting acceleration, there are a piezoresistive type, an electrostatic capacitance type and the like. This type of semiconductor acceleration sensor has a structure having a movable portion and a fixed portion on a semiconductor substrate, and is formed so that a minute displacement is generated between the movable portion and the fixed portion when an acceleration acts. . Acceleration can be detected by electrically detecting this minute displacement by a detection means formed between the movable portion and the fixed portion, for example, a piezoresistor or a condenser.

FIG. 4 shows an electrostatic capacitance type semiconductor acceleration sensor proposed in Japanese Patent Laid-Open No. 10-115635. This is a semiconductor substrate 100,
The semiconductor substrate 200 is mounted on this.

The semiconductor substrate 100 is made of silicon, and the weight portion 11 separated from the semiconductor substrate 100 is used.
0, and a thin-walled suspension part 120 continuous from one side thereof is formed. A movable electrode 130 is provided on the upper surface of the ridge portion 110.
However, the electrostatic attraction electrode 140 and the wiring 150 of the movable electrode 130, which are independent of the movable electrode 130, are formed on the upper surface of the suspension part 120, respectively, and are formed by doping impurities or depositing metal. ing. Further, the wiring 150 and the electrode pad 160 are formed on the semiconductor substrate 100 by doping impurities or depositing metal.

Like the semiconductor substrate 100, the semiconductor substrate 200 is made of silicon, and a recess 210 having a flat bottom surface is formed on the back surface at a predetermined depth position. Further, a fixed electrode 220 is formed on the back surface at a position facing the movable electrode 130, an electrostatic attraction electrode 230 is formed on the bottom surface of the recess 210 at a position facing the electrostatic attraction electrode 140, and a wiring 250 for each electrode is formed. Like the semiconductor substrate 100, it is formed by doping impurities or depositing a metal. The wiring 240 is obtained by filling a via hole 250 provided in the vicinity of an end portion of the semiconductor substrate 200 with a conductive resin 260 such as a conductive epoxy resin.
Is connected to an external wiring (not shown) via a bonding wire (not shown). The electrostatic attraction electrode 230 of the semiconductor substrate 200 is formed in the recess 210, and by adjusting the depth of the recess 210, a predetermined gap is provided between the electrostatic attraction electrode 140 and the electrostatic attraction electrode 140 facing the movable electrode 130. Are formed.

The semiconductor substrate 10 thus formed
The movable electrodes 130, the fixed electrodes 220, and the electrostatic attraction electrodes 140 and 230 are overlapped with each other and bonded to each other, and are housed in a ceramic package (not shown) so that the bonding wires and the conductive resin 260 can be removed. The semiconductor acceleration sensor is completed by connecting to the external wiring via.

According to this semiconductor acceleration sensor, the displacement amount of the weight portion 110, which is relatively displaced in the thickness direction of the semiconductor substrate 100 due to the applied acceleration, is determined by the static capacitance of the capacitor composed of the movable electrode 130 and the fixed electrode 220. The acceleration can be detected by converting the electric signal by the electric capacity and taking out the electric signal. Further, by changing the voltage applied to the electrostatic attraction electrodes 140 and 230, the attraction force between the electrodes 140 and 230 is changed, and the balance between the action of the inertial force exerted by these accelerations and the electrostatic force. Can be changed to adjust the sensitivity of the semiconductor acceleration sensor.

[0008]

By the way, in general,
In the semiconductor acceleration sensor, there are variations in the initial position thereof due to the warp of the weight portion 110 in the manufacturing process,
As a result, the output (offset) when acceleration is not applied varies. In order to set this offset to a predetermined value and perform accurate acceleration detection, an arbitrary voltage is applied between the electrostatic attraction electrodes 140 and 230,
The voltage and the detected signal can be solved by, for example, computing. In the conventional case, when the weight portion 110 is warped in the direction of the semiconductor substrate 100 (upward direction in FIG. 4), the weight is reduced. Since the portion 110 is pushed by the semiconductor substrate 200, the offset is apparently constant, and it is not necessary to apply an arbitrary voltage between the electrostatic attraction electrodes 140 and 230. However, since the weight portion 110 is applied with a pressing force from the semiconductor substrate 200, the sensitivity of acceleration detection changes, and even if the same acceleration is applied, the displacement amount varies, resulting in accuracy. There is a risk that it will be difficult to perform good acceleration detection.

The present invention has been made in view of the above points, and it is an object of the present invention to adjust the sensitivity to acceleration and to improve the accuracy of acceleration detection by suppressing the displacement variation of the weight portion. Another object is to provide a semiconductor acceleration sensor.

[0010]

In order to achieve the above object, a semiconductor acceleration sensor according to a first aspect of the present invention includes a supporting portion provided by etching a semiconductor substrate, and a supporting portion having a movable electrode. A weight portion that is displaced relative to the weight portion, a suspension portion that projects from a predetermined side of the support portion to elastically support the weight portion, and a suspension portion that is provided on the surface of the suspension portion and that corresponds to the displacement amount of the weight portion. A strain gauge resistance whose resistance value displaces, and a stopper which is provided in the support portion, regulates the maximum displacement of the weight portion, and has a fixed electrode at a position facing the movable electrode provided in the weight portion. In a semiconductor acceleration sensor, a displacement control circuit that applies a voltage between the movable electrode and the fixed electrode to control displacement of the weight portion, and an arithmetic circuit that calculates an acceleration signal based on an output from the displacement control circuit. It is characterized by having and.

According to a second aspect of the present invention, in the semiconductor acceleration sensor of the first aspect, the displacement control circuit adjusts at least a sensitivity setting circuit for adjusting the sensitivity of the detected acceleration and an initial position of the weight portion. An initial position adjustment circuit,
A voltage control circuit for controlling the displacement voltage based on the signals from the sensitivity setting circuit and the initial position adjusting circuit is provided.

According to a third aspect of the present invention, in the semiconductor acceleration sensor of the first or second aspect, the initial position adjusting circuit includes at least a comparator and a counter.

According to a fourth aspect of the present invention, in the semiconductor acceleration sensor according to any one of the first to third aspects, the voltage control circuit includes at least a digital-analog converter and a pulse modulation circuit.

According to a fifth aspect of the present invention, in the semiconductor acceleration sensor according to any one of the first to fourth aspects, the movable electrode is provided on both surfaces of the weight portion, and the stopper having the fixed electrode is provided. It is supposed to be provided on both sides of the supporting portion.

A semiconductor acceleration sensor according to a sixth aspect of the present invention is the semiconductor acceleration sensor according to any one of the first to fifth aspects, wherein a plurality of the movable electrodes are arranged in a direction that is not at least parallel to the protruding direction of the suspension portion. I am supposed to.

A semiconductor acceleration sensor according to a seventh aspect of the present invention is the semiconductor acceleration sensor according to any one of the first to sixth aspects, wherein a plurality of the fixed electrodes are arranged in a direction that is not at least parallel to the protruding direction of the suspension portion. I am supposed to.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing a semiconductor acceleration sensor according to the present embodiment. Further, FIG. 2 shows the sensor chip,
(A) is a plan view of a state where the upper stopper is removed, (b) is a cross-sectional view thereof, and (c) is a plan view of the upper stopper.

The semiconductor acceleration sensor of this embodiment mainly comprises a sensor chip 1, a displacement control circuit 2 and an arithmetic circuit 3, of which the sensor chip 1 includes a support portion 11, a weight portion 12 and a suspension portion. The displacement control circuit 2 includes a voltage control circuit 4, an initial position adjusting circuit 5, and a strain gauge resistor 14 and stoppers 15 and 16.
And a sensitivity setting circuit 6.

The supporting portion 11 serves as a frame of the semiconductor acceleration sensor, and is formed of, for example, a semiconductor substrate made of silicon, and is a frame body having a substantially rectangular shape in plan view. Further, it has substantially quadrangular slits 11d and 11d formed in the center thereof. Further, at a predetermined position on the surface (upper side in FIG. 2) on which a suspension portion 13 is formed, which will be described later, for example, wirings 11a and 11b formed by diffusing aluminum (Al) or impurities, and, for example, aluminum are used. The electrode pad 11c is formed, and the wirings 11a and 11b and the electrode pad 11c are electrically connected.

The weight portion 12 is displaced in the direction of the acting acceleration and transmits its magnitude to the strain gauge resistor 14 described later, and is formed of, for example, a semiconductor substrate made of silicon. Its shape is a quadrangle in plan view, and an inverted trapezoidal mass whose lower surface is smaller than its upper surface in cross-sectional view. This one has slits 11d, 11
is disposed on the same plane as the support portion 11 via d,
The suspension portion 13 is supported so as to swing with respect to the support portion 11. Further, on the upper and lower surfaces (vertical direction in FIG. 2), for example, the movable electrodes 12a, 1 made of aluminum are formed.
2b has the same size as the lower surface of the weight portion 12 and is formed in a substantially quadrangular film shape. In addition, a wiring 11e for applying a voltage to the movable electrode 12a, which is formed by diffusing impurities, for example, is formed from the support portion 11 through the suspension portion 13. Further, although not shown, a wiring for applying a voltage to the movable electrode 12b, for example, formed by diffusing impurities, is formed on the lower surface of the semiconductor substrate from the supporting portion 11 through the suspension portion 13. ing.

The suspension portion 13 elastically (oscillates) supports the weight portion 12 with respect to the support portion 11,
For example, it is formed of a semiconductor substrate made of silicon. Its shape is a substantially quadrangular shape in a plan view, and is formed in a thin-walled flat plate shape. This is the electrode pad 1
For example, two protrusions are provided from one side of the support portion 11 forming the 1c toward the inside thereof, and are integrally formed with the weight portion 12.

The strain gauge resistor 14 converts the displacement amount of the weight portion 12 displaced by the applied acceleration into an electric signal, and is formed of, for example, a diffusion resistor in which impurities are diffused. This is embedded in the surface of the suspension portion 13, and one suspension portion 13 forms, for example, two strain gauge resistors 14. Further, this one constitutes a Wheatstone bridge on the suspension portion 13,
It is wired so as to output an electric signal proportional to the magnitude of the applied acceleration. Then, it is electrically connected to the electrode pad 11c through the wirings 11a and 11b.

The stoppers 15 and 16 are provided to prevent excessive displacement of the weight 12 when acceleration exceeding the rating acts on the weight 12 to prevent damage. For example, a semiconductor substrate made of heat-resistant glass or the like. It is made of a glass material having a coefficient of thermal expansion close to. Its shape is a plate body that is substantially quadrangular in a plan view. This member is joined to the upper and lower surfaces of the support portion 11 at predetermined positions so as to cover the weight portion 12. In addition, fixed electrodes 15a and 16a made of, for example, aluminum are formed in a substantially quadrangular film shape in the same size as the movable electrodes 12a and 12b at positions of the stoppers 15 and 16 facing the movable electrodes 12a and 12b. . Further, a wiring 15b made of, for example, aluminum for applying a voltage to the fixed electrode 15a is formed on the formation surface thereof. Although not shown, the stopper 16 is also formed with a wiring made of, for example, aluminum for applying a voltage to the fixed electrode 16a.

The voltage control circuit 4 includes movable electrodes 12a, 12
b to output voltage to the fixed electrodes 15a and 16a, and the weight 1
2, which changes the sensitivity to the initial position or acceleration, and is connected to the sensor chip 1 and an initial position adjusting circuit 5 described later as well as a sensitivity setting circuit 6 described later. This is composed of, for example, a digital-analog converter (not shown) and a pulse width modulation circuit (not shown). In this device, a digital signal output from the initial position adjusting circuit 5 is converted into a voltage applied to the movable electrodes 12a and 12b and fixed electrodes 15a and 16a by a digital-analog converter, and the voltage is further converted by a pulse width modulation circuit. Movable electrodes 12a, 12b converted into pulse signals
Also, the weight 12 is forcibly displaced by applying it to the fixed electrodes 15a and 16a. Also, the sensitivity setting circuit 6
The digital signal for controlling the amount of displacement of the weight 12 output from the movable electrode 12 is output by the digital-analog converter.
a, 12b and the fixed electrodes 15a, 16a are converted into a voltage to be applied, and the voltage is further converted into a pulse signal by a pulse width modulation circuit and applied to the movable electrodes 12a, 12b and the fixed electrodes 15a, 16a. The sensitivity of the weight 12 to acceleration is changed. Here, the displacement mechanism of the weight 12 will be described. The movable electrode 12a and the fixed electrode 15a and the movable electrode 12b and the fixed electrode 16a form a kind of capacitor, and when a voltage is applied to the movable electrodes 12a and 12b and the fixed electrodes 15a and 16a, a static capacitance is generated between the two electrodes. Electricity is generated. Here, when the electrode area is S, the interelectrode distance is L, the voltage between the electrodes is V, and the dielectric constant between the electrodes is ε, the electrostatic force Fe acting between both electrodes is represented by: This electrostatic force changes the initial position of the weight portion 12, and as a result, the offset voltage can be adjusted. Also,
This electrostatic force also acts as a force that suppresses displacement of the weight portion 12 with respect to acceleration, and as a result, the sensitivity of acceleration can be changed.

The initial position adjusting circuit 5 adjusts the initial position of the weight portion 12 in order to minimize the offset of the semiconductor acceleration sensor, and is connected to the sensor chip 1 and the voltage control circuit 4. This is at least a comparator 5
The output voltage (offset voltage) from the sensor chip 1 in a state where no acceleration is applied is input to the comparator 5a. Comparator 5
The reference voltage (intermediate voltage of the output range (for example, 0 V when the output range is ± 1 V)) is set in a,
When the offset voltage is larger than the reference voltage by comparing the offset voltage and its magnitude relationship, the counter 5b is set to High.
The signal of h is output, and when it is small, the signal of Low is output. The counter 5b increments the count value when a High signal is input, decrements the count value when a Low signal is input, and outputs the count value to the voltage control circuit 4 each time. Then, in this comparison, the High and Low signals are alternately applied to the counter 5b.
Are repeatedly input to the arithmetic circuit 3 described later as a correction signal for the acceleration calculation until the time when the offset voltage becomes the same level as the reference voltage.

The sensitivity setting circuit 6 sets the sensitivity of the semiconductor acceleration sensor, and is connected to the voltage control circuit 4 and the arithmetic circuit 3. This is, for example, using a logic circuit or the like to convert an arbitrary sensitivity setting value input by an input device such as a keyboard into a predetermined digital signal according to the setting sensitivity and outputting the digital signal to the voltage control circuit 4. is doing. By the way, when acceleration acts on the weight 12,
Between the movable electrode 12a and the fixed electrode 15a and the movable electrode 12b
The sensitivity may change due to a change in the distance between the fixed electrode 16a and the fixed electrode 16a. This is because the electrostatic force is inversely proportional to the square of the distance, and in order to suppress this change in sensitivity (change in electrostatic force), the sensitivity that changes due to the displacement of the weight portion 12 when acceleration acts is It is kept constant by changing the voltage between the electrodes. Further, the digital signal of the sensitivity setting is output to the arithmetic circuit as a correction signal for acceleration calculation.

The arithmetic circuit 3 calculates the signal output from the sensor chip 1 and outputs an acceleration signal.
It is connected to the sensor chip 1 and the sensitivity setting circuit 6. This device calculates a signal output from the sensor chip 1 and a correction signal set based on the digital signal output from the sensitivity setting circuit 6, and outputs an acceleration signal according to the set sensitivity.

Next, the operation will be described.

First, the initial position adjusting circuit 5 inputs the offset voltage from the sensor chip 1 to the comparator 5a and compares it with the reference voltage. The result is output to the counter 5b, and the count value of the counter 5b is output to the voltage control circuit 4. The voltage control circuit 4 displaces the initial position of the weight portion 12 based on this count value. By repeating this operation, when the difference between the offset voltage and the reference voltage becomes the minimum, the displacement of the weight portion 12 is terminated and the count value at that time is output to the arithmetic circuit 3. Then, the sensitivity setting circuit 6
The sensitivity setting value input from an input device such as a keyboard
For example, using a logic circuit or the like, it is converted into a predetermined digital signal according to the set sensitivity and output to the voltage control circuit 4,
At the same time, the digital signal is output to the arithmetic circuit 3. Next, the voltage control circuit 4 uses the digital-analog converter to convert the digital signals from the initial position adjustment circuit 5 and the sensitivity setting circuit 6 into movable electrodes 12a and 12b and fixed electrodes 15a and 15a.
16a is converted into a voltage to be applied to the movable electrode 12, and the voltage is converted into a pulse signal by a pulse width modulation circuit.
a, 12b and the fixed electrodes 15a, 16a, the weight 12 is forcibly displaced and the weight 12
Change the sensitivity to acceleration.

On the other hand, when acceleration is applied to the sensor chip 1, the weight portion 12 is relatively displaced in the thickness direction of the support portion 11. At this time, the strain gauge resistor 14 is distorted due to the bending of the suspension portion 13, and thus the balance of the Wheatstone bridge is disturbed, and an electric signal corresponding to the acting acceleration is output from the sensor chip 1 to the arithmetic circuit 3. However, since this electric signal is a signal according to the amount of bending of the suspension portion 13, even if the sensitivity to acceleration is changed, the displacement amount of the weight portion 12 is regulated by the stoppers 15 and 16, so that the sensor chip can The absolute value of the output electric signal does not change. However, the calculation circuit 3 sets a correction signal based on the count values from the initial position adjustment circuit 5 and the sensitivity setting circuit 6 and calculates the electrical signal output from the sensor chip 1 to obtain the sensitivity according to the set sensitivity. The acceleration signal can be output.

According to the semiconductor acceleration sensor described above, the sensitivity setting circuit 6 for adjusting the sensitivity of at least the detected acceleration, the initial position adjusting circuit 5 for adjusting the initial position of the weight portion 12, the sensitivity setting circuit 6, and the initial position adjustment. By providing the displacement control circuit 2 including the voltage control circuit 4 that controls the displacement voltage based on the signal of the circuit 5, and the arithmetic circuit 3 that calculates the acceleration signal based on the output from the displacement control circuit 2, Movable electrodes 12a, 12b and fixed electrodes 15a, 1
Since it becomes possible to easily adjust the electrostatic force acting on the weight portion 12 by changing the voltage applied to the 6a, the displacement amount with respect to the sensitivity of the weight portion 12 can be easily adjusted, and one semiconductor acceleration sensor can be used. The acceleration detection range can be set arbitrarily. Further, since the initial position of the weight portion is adjusted by the count value of the counter 5b to minimize the offset voltage, the accuracy of acceleration detection can be improved and the voltage superimposed on the acceleration detection signal can be reduced. This makes it possible to have a large range for sensitivity.

The voltage control circuit 4 is not limited to the pulse width modulation circuit, but may be formed by a pulse amplitude modulation circuit, for example.

[Second Embodiment] FIG. 3 shows a sensor chip of a semiconductor acceleration sensor according to the present embodiment. FIG. 3A is a plan view showing a state where an upper stopper is removed,
(B) is the sectional view, and (c) is a plan view of the upper stopper.

In the semiconductor acceleration sensor of this embodiment, the movable electrode and the fixed electrode are different from those of the first embodiment.
The other components are substantially the same as those in the first embodiment, and thus the description thereof will be omitted. Further, the same members are given the same numbers as in the first embodiment.

The movable electrodes 12c and 12d are the movable electrodes 12
Similar to a and 12b, the weight 12 is formed on the upper and lower surfaces (vertical direction in FIG. 3) of, for example, aluminum, and is formed in a substantially quadrangular film shape in a plan view. A plurality of these are arranged in a direction orthogonal to the protruding direction of the suspension portion 13. Further, a wiring 11e for applying a voltage to the movable electrode 12c, which is formed by diffusing impurities, for example, is formed from the support portion 11 through the suspension portion 13. Although not shown, for example, for applying a voltage to the movable electrode 12d on the lower surface of the semiconductor substrate,
The wiring formed by diffusing impurities is the supporting portion 11
Is formed through the suspension portion 13.

The fixed electrodes 15c and 16b are the stopper 1
At positions facing the movable electrodes 12c and 12d of 5 and 16,
For example, the movable electrode 1 is made of aluminum.
It is formed in the shape of a film having the same size as 2c and 12d and forming a substantially square shape. A plurality of these are arranged in a direction orthogonal to the protruding direction of the suspension portion 13. A wiring 15d made of, for example, aluminum for applying a voltage to the fixed electrode 15c is formed on the formation surface thereof. Although not shown, the stopper 16 is also provided with a wiring made of, for example, aluminum for applying a voltage to the fixed electrode 16b.

According to the semiconductor acceleration sensor described above, it is possible to individually apply a voltage to each of the electrodes 12c, 12d, 15c, 16b. Therefore, by adjusting the applied voltage, the static voltage in the plane of the weight portion 12 can be adjusted. The power is applied in a uniform manner, and the sensitivity can be adjusted with higher accuracy.

A plurality of movable electrodes 12c and 12d or fixed electrodes 15c and 16b may be provided. The size of the weight 12
It is not limited to the same size as the bottom surface of. Also,
Movable electrodes 12c and 12d and fixed electrodes 15c and 16b
Is not limited to the strip body orthogonal to the protruding direction of the suspension portion 13, and may be formed in a dogleg shape, for example.

[0040]

In order to achieve the above object, the semiconductor acceleration sensor of the invention according to claim 1 is a displacement control circuit for applying a voltage between a movable electrode and a fixed electrode to control the displacement of the weight portion. And an arithmetic circuit that calculates an acceleration signal based on the output from the displacement control circuit, the magnitude of the electrostatic force generated between both electrodes can be changed by a predetermined circuit. It becomes possible to adjust the displacement amount of the weight portion, and it becomes possible to arbitrarily set the acceleration detection range with one semiconductor acceleration sensor. Further, since it is possible to correct the variation in the initial position of the weight portion, it is possible to improve the accuracy of detecting the acceleration.

In addition to the effect of claim 1, the semiconductor acceleration sensor of the invention according to claim 2 includes a displacement control circuit, a sensitivity setting circuit for adjusting at least the sensitivity of detected acceleration, and an initial position for adjusting the initial position of the weight portion. By providing the position adjustment circuit and the voltage control circuit that controls the displacement voltage based on the signals of the sensitivity setting circuit and the initial position adjustment circuit, the voltage applied between the movable electrode and the fixed electrode can be easily controlled. Therefore, the electrostatic force for setting the sensitivity of the weight can be easily adjusted. Further, since the initial position of the weight portion is adjusted to minimize the offset voltage, the voltage superimposed on the acceleration detection signal can be reduced, and the range with respect to the sensitivity can be widened.

According to the semiconductor acceleration sensor of the third aspect of the invention, in addition to the effect of the first or second aspect, the initial position adjusting circuit is composed of at least a comparator and a counter, so that the count value of the counter Since the voltage applied to the movable electrode and the fixed electrode can be controlled, it is possible to easily set the initial position of the weight portion where the offset voltage becomes the minimum.

According to the semiconductor acceleration sensor of the fourth aspect of the present invention, in addition to the effect of any one of the first to third aspects, the voltage control circuit is composed of at least a digital-analog converter and a pulse modulation circuit, whereby the movable electrode and the fixed electrode are fixed. Since the instability of the voltage value due to noise or the like can be reduced as compared with the case where the amplitude (magnitude) of the voltage applied to the electrodes is changed, the accuracy of acceleration detection can be made higher.

In addition to the effect of any one of claims 1 to 4, the semiconductor acceleration sensor of the invention according to claim 5 has movable electrodes on both sides of the weight portion, and stoppers having fixed electrodes on both sides of the support portion. By providing the displacement control of the weight portion in two directions, the sensitivity can be accurately adjusted.

According to the semiconductor acceleration sensor of the sixth aspect of the present invention, in addition to the effect of any one of the first to fifth aspects, by disposing a plurality of movable electrodes in a direction at least not parallel to the protruding direction of the suspension portion, Since a voltage can be applied individually to each electrode, it is possible to make uniform the way in which the electrostatic force is applied within the surface of the weight portion, and it is possible to adjust the sensitivity with higher accuracy.

According to the semiconductor acceleration sensor of the seventh aspect of the present invention, in addition to the effect of any one of the first to sixth aspects, by arranging a plurality of fixed electrodes in a direction at least not parallel to the protruding direction of the suspension portion, Since a voltage can be applied individually to each electrode, it is possible to make uniform the way in which the electrostatic force is applied within the surface of the weight portion, and it is possible to adjust the sensitivity with higher accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a semiconductor acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a sensor chip of the above, FIG.
Is a plan view with the upper stopper removed, (b) is a cross-sectional view thereof, and (c) is a plan view of the upper stopper.

3A and 3B are diagrams showing a sensor chip of a semiconductor acceleration sensor according to a second embodiment of the present invention, FIG. 3A is a plan view without an upper stopper, and FIG.
(C) is a plan view of the upper stopper.

FIG. 4 is a sectional view showing a conventional semiconductor acceleration sensor.

[Explanation of symbols] 1 sensor chip 2 Displacement control circuit 3 arithmetic circuit 4 Voltage control circuit 5 Initial position adjustment circuit 5b counter 5a comparator 6 Sensitivity setting circuit 11 Support 12 Weight 12a movable electrode 12b movable electrode 12c movable electrode 12d movable electrode 13 Suspension section 14 gauge resistance 15 Stopper 15a fixed electrode 15b wiring 15c fixed electrode 15d wiring 16 stopper 16a fixed electrode 16b fixed electrode

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4M112 AA02 BA01 CA21 CA22 CA24                       CA28 CA30 CA32 DA12 EA02                       EA11 EA13 FA01 FA03 FA07

Claims (7)

[Claims] 1. A support part formed by etching a semiconductor substrate, a weight part having a movable electrode and relatively displaced with respect to the support part, and a weight part projecting from a predetermined side of the support part. The suspension part that elastically supports the strain gauge, the strain gauge resistance that is provided on the surface of the suspension part and whose resistance value changes according to the displacement amount of the weight part, and the maximum displacement amount of the weight part that is provided on the support part are restricted. Then, a voltage is applied between the movable electrode and the fixed electrode to a sensor chip provided with a stopper having a fixed electrode at a position facing the movable electrode provided in the weight portion, and a voltage is applied between the movable electrode and the fixed electrode. A semiconductor acceleration sensor, comprising: a displacement control circuit that performs displacement control; and a calculation circuit that calculates an acceleration signal based on an output from the displacement control circuit. 2. The displacement control circuit is based on at least a sensitivity setting circuit for adjusting the sensitivity of the detected acceleration, an initial position adjusting circuit for adjusting the initial position of the weight portion, and signals based on the sensitivity setting circuit and the initial position adjusting circuit. 2. The semiconductor acceleration sensor according to claim 1, further comprising a voltage control circuit that controls the displacement voltage. 3. The semiconductor acceleration sensor according to claim 1, wherein the initial position adjustment circuit includes at least a comparator and a counter. 4. The semiconductor acceleration sensor according to claim 1, wherein the voltage control circuit includes at least a digital-analog converter and a pulse modulation circuit. 5. The semiconductor acceleration sensor according to claim 1, wherein the movable electrode is provided on both surfaces of the weight portion, and the stopper having the fixed electrode is provided on both surfaces of a support portion. 6. The plurality of movable electrodes are arranged at least orthogonally to the protruding direction of the suspension portion.
The semiconductor acceleration sensor according to any one of claims. 7. A plurality of the fixed electrodes are arranged at least orthogonal to a protruding direction of the suspension portion.
The semiconductor acceleration sensor according to any one of claims.