JPH1138038A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor having a new structure and stable performance at a low cost by digitally calculating signals from electrodes with a sensor head having three fixed electrodes, and detecting the acceleration in three axial directions. SOLUTION: A metal electrode is formed on one face of a glass substrate as a fixed electrode layer 20, it is uniformly divided into three on a circumference with the required radius centering on the Z-axis to arrange three electrodes, and a silicon substrate is machined to form a flexible substrate layer 21 to form electrostatic capacity elements C1 -C3 arranged with three electrode pairs face to face in the X-axis direction. A heavy bob body 23 is connected beneath a moving electrode, and a silicone substrate layer 24 constituted of a pedestal layer 22 for securing a moving space and a stopper at the time of an overload is laminated to manufacture an electrostatic capacity type acceleration sensor with a four-layer structure. The fixed electrode layer 20 of a glass plate arranged on the face opposite to the flexible substrate layer 21 is provided with electrode lead pads on the flexible substrate layer 21 from peripheral notch gaps to connect leads 26 to the outside from the electrodes on the opposite faces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor having a novel structure, in which the processing accuracy in manufacturing governs the measurement accuracy of the sensor, and a linearity error occurs due to structural restrictions, resulting in a complicated correction. The present invention relates to an acceleration sensor including a capacitance type having a simple configuration of a three-electrode structure in order to solve the problem of the conventional acceleration sensor in which the above-mentioned is indispensable.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open Nos. 4-148833 and 4-33743 disclose capacitive acceleration sensors.
No. 1, Japanese Patent Application Laid-Open No. Hei 5-18879 discloses that a plurality of pairs of capacitance elements are provided on opposite surfaces of a fixed substrate and a flexible substrate and electrodes are attached to each other, and an XY parallel to the substrate surface is provided. A plane is set, and changes in acceleration in the three-dimensional directions of the X, Y, and Z axes of the Z axis orthogonal to the plane are calculated based on capacitance changes between a plurality of pairs of capacitance elements. There has been proposed a configuration for performing detection.

For example, as shown in a vertical section of FIG. 13B,
A fixed substrate 11 arranged in a cylinder 10 in a diametric direction, and a flexible substrate 12 arranged in parallel with a predetermined interval provided therebetween;
As shown in FIG. 13A showing a lower surface of the fixed substrate 11, to form an electrostatic capacitance element C ₁ -C ₅ and clamped by the respective electrodes 5 to each opposing surface between the fixed substrate 11 and the flexible substrate 12 It consists of a configuration. An actuator 13 having an appropriate mass and serving as a weight is provided on the lower surface of the flexible substrate 12.

In detail, here, four pairs of electrodes are provided on the outer peripheral portion between the opposing surfaces, and one pair of electrodes are provided
Configuration to form a ₁ -C _5, i.e., perpendicular with the electrode surface X, each two capacitances arranged on two axes of Y element C
And ₁ -C _4, consisting of construction of arranging the capacitive element C ₅ in the middle of the previous two axes.

In the above configuration, when acceleration is applied in the X-axis direction, as shown in FIG. 14A, the flexible substrate 12 having the actuator 13 is deformed, and
Since the distance between each of the electrodes 1 to 5 between the surfaces facing the flexible substrate 12 and the flexible substrate 12 changes, the capacitance of each of the capacitance elements C _{1 to} C ₄ changes. Also, as shown in FIG. 14B, when acceleration is applied in the Z-axis direction, the capacitance of each of the capacitance elements C _{1 to} C ₄ similarly changes.

[0006] The detection of each component of the acceleration based on the change in the capacitance is performed, for example, as an output with respect to the acceleration in the X-axis direction, as a capacitance difference (C ₁ -C ₃ ) between the capacitance elements C ₁ and C ₃ , As outputs for the acceleration in the Y-axis direction, the capacitance elements C ₂ and C ₄
Is detected as the capacitance (C ₅ ) of the capacitance element C ₅ as an output with respect to the capacitance difference (C ₂ −C ₄ ) and acceleration in the Z-axis direction.

[0007]

[SUMMARY OF THE INVENTION In the electrostatic capacitance type acceleration sensor having the above structure, X calculated in the electric signal proportional to the electrostatic capacitance of the capacitance element C ₁ ~C _5, Y, the output of the Z-axis Strictly speaking, there is a problem that the acceleration does not have linearity. Further, in this case, there is a problem that the sensitivity of the X and Y axis outputs depends on the Z axis output. Further, when the initial value d ₀ of the electrode gap changes due to a temperature change or the like, the value of 0 on the Z axis is changed.
There is a problem that a sensitivity shift in the X, Y, and Z axes occurs in addition to the point shift.

Further, in the capacitance type acceleration sensor having the above configuration, even when the calculation is performed using an electric signal inversely proportional to the capacitance elements C _{1 to} C ₅ , stray capacitance other than the capacitance of the sensor cannot be ignored. Therefore, the various problems described above occur.

[0009] The problems in the 4-5 electrode system will be described below in detail. The X (Y) -axis acceleration is detected from the difference between the capacitances of the two electrodes arranged on the detection axis, but actually takes the difference between the CV-converted outputs. In that case, no matter what CV conversion method that can be generally adopted, the following linearity error theoretically occurs, and it is impossible to detect X, Y and Z completely independently. Will be possible.

[0010]

(Equation 1)

Where do: initial gap distance dx: change amount due to x acceleration (amount proportional to acceleration) dz: change amount due to z acceleration (amount proportional to acceleration)

In this sensor, the physical quantity that can be expected to be proportional to the acceleration is the amount of change in the distance between the electrodes, and it cannot be expected that the capacitance changes linearly with the acceleration.

As a representative example 1 of the linearity error, 1 / C → V
May be converted to In reality, the sensor capacitance C means not only the counter electrode capacitance (theoretical sensor capacitance) but also a finite stray capacitance (inside the sensor and the circuit portion). CV conversion is performed as the sum of Therefore, the stray capacitance becomes a nonlinear term, and a linearity error occurs. Other axis interference occurs in which the linearity of the X, Y, and Z outputs is degraded, and the Z acceleration affects the sensitivity of X and Y.

As a second representative example of the linearity error, there is a case of CV proportional conversion. As is apparent from the above equation, since the amount proportional to the acceleration is in the denominator of C, in the case of the CV proportional conversion, the output voltage does not change linearly with the acceleration. Therefore, the linearity degradation of the X, Y, and Z outputs and the sensitivity of X, Y
Other axis interference, which is affected by acceleration, occurs.

[0015]

(Equation 2)

[0016]

(Equation 3)

Since there is a problem of the two linearity errors described above, if accuracy is required, some subsequent correction is required. With respect to the correction, in the case of the above-described representative example 1, the true X,
It is difficult to obtain the Y and Z accelerations by the correction calculation.

Further, in the case of the above-mentioned representative example 2, a correction calculation method was proposed (Japanese Patent Laid-Open No. Hei 8-313552). However, in order to perform strict correction, a very complicated calculation formula is required. Compensation is particularly complicated when the correction calculation is performed, including the other axis sensitivity, main axis sensitivity, and zero point due to the processing error, which are the correction (adjustment) terms of, for example, in the physical sensor workshop of the Institute of Electrical Engineers of Japan. Document (1996 11
As described in the document No. PS-96-15 “Correction of Capacitance Type Three Axis Acceleration Sensor” published on the 11th and 12th of May, correction calculation using an approximate expression is performed. However, in this case, the error due to the approximation may not be negligible, and this method may not be able to satisfy the demand for higher precision.

In the conventional acceleration sensor, the X and Y detection axes are determined by the arrangement of the four fixed electrodes, and the Z axis is determined by the arrangement of the movable electrode surface. Further, since the processing error appears as the sensitivity of the other axis, a very high-precision processing technique is required.

That is, in the conventional acceleration sensor, X,
The Y-detection axis is determined by the arrangement of the four fixed electrodes, and the Z-axis is determined by the arrangement of the movable electrode surface. Further, since the processing error appears as the sensitivity of another axis, a problem of linearity error occurs. Some kind of correction is indispensable, and complicated calculations are required for the correction, and the precision in the manufacturing process of the sensor is severe and there is a limit in performing the strict correction, and such an acceleration sensor is manufactured stably and in large quantities. It was extremely difficult.

According to the present invention, the conventional acceleration sensor has a problem of linearity error due to structural restrictions, and complicated correction is indispensable. In addition, the processing accuracy in manufacturing dominate the measurement accuracy of the sensor. In consideration of the reality, a problem of a linearity error hardly occurs, and an acceleration sensor including a capacitance type having a novel configuration is provided so that processing accuracy in manufacturing does not determine measurement accuracy of the sensor. The purpose is.

[0022]

As a result of various studies on a configuration in which the problem of linearity error is unlikely to occur and the processing accuracy in manufacturing does not determine the measurement accuracy of the sensor,
By using a sensor head having three fixed electrodes to digitally calculate signals from each electrode, it is possible to detect accelerations in three directions orthogonal to X, Y, and Z, thereby achieving the object. XY- specified on the sensor
3-axis accelerations Ax, Ay, A acting on the Z orthogonal coordinate system
An acceleration sensor including a capacitance type composed of three electrode pairs having at least one electrode pair having sensitivity to each acceleration with respect to z was completed.

Further, the present inventor proposes an acceleration sensor having the above configuration, wherein the centroid of the plane shape of each electrode is not on the same straight line in the XY coordinate system plane, and the centroid of the plane shape of each electrode. Are respectively located at three equally divided positions on the Z-axis center on the XY coordinate system plane, and XY
An acceleration sensor is also characterized in that three electrodes are arranged on a coordinate system plane on a circumference of a required radius centered on the Z axis and divided into three equal parts, and three electrode pairs are arranged facing each other in the Z axis direction. To suggest.

Further, the inventor of the present invention has proposed a movable electrode in which a weight is provided on the lower surface of a movable portion of a flexible substrate having a beam-supporting structure, the upper surface is arranged to face the fixed substrate, and the electrode is arranged on the upper surface of the movable portion. A means for detecting the relative position from the initial position including the inclination of the movable electrode, and the accelerations Ax and Ay in the three axial directions based on the position information of the electrodes. , Az are also proposed.

In addition, the present inventors, in an acceleration sensor in which the same laminated structure as described above is of a capacitance type, a fixed electrode layer in which three metal electrodes are formed in a required pattern on the lower surface of a glass layer. A flexible substrate layer having a weight body with a relatively thick movable portion formed by providing a supporting structure by patterning on a semiconductor substrate supported by a beam around the flexible substrate layer, and a flexible substrate layer are mounted thereon. The present invention also proposes a capacitance type acceleration sensor having a three-layer structure including a silicon layer serving as a stopper when a weight body comes into contact when overloaded.

In addition, in the above-mentioned capacitance type acceleration sensor, the inventor has stated that the glass layer has a conical or pyramid-shaped through hole provided in a required pattern, and the conduction of the metal electrode on the lower surface is performed through the through hole. The configuration to be performed, a glass substrate having a conical or pyramid-shaped through-hole provided in a required pattern and a semiconductor substrate are joined together on both sides of a composite plate on the conical top side of the through-hole. In addition, the present invention proposes a capacitance type acceleration sensor having a configuration in which a composite plate layer having a configuration in which electric conduction is carried out via a semiconductor is joined to an upper surface of a flexible substrate layer by bonding electrodes so as to face each other and the inside of which is sealed.

Further, the inventor has found that a fixed electrode layer in which metal electrodes are formed in a required pattern on the lower surface of the glass layer for three electrodes, and that the upper surface is supported by a beam and the upper surface is spaced from the electrode by a predetermined gap. A movable electrode layer made of silicon, which is disposed to face and is movable up and down so as to form a common electrode; a pedestal layer which supports the periphery of the movable electrode layer and a weight joined by anodic bonding below the movable electrode; The present invention also proposes a capacitance type acceleration sensor having a four-layer structure including a silicon layer serving as a stopper when a weight joined to a layer comes into contact with an overload.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A three-axis acceleration sensor according to the present invention employs a conventional method of obtaining the X, Y, and Z outputs by taking the difference or sum of signals from four or five fixed electrodes. On the other hand, on the premise that signals from the respective electrodes are digitally operated, acceleration is detected in directions of three axes orthogonal to X, Y, and Z using a sensor head having three fixed electrodes. .

The structure of the conventional three-axis acceleration sensor is the same as that of the conventional three-axis acceleration sensor except for the structure of the fixed electrode, and includes a fixed electrode arranged in the same plane and a movable electrode arranged substantially parallel to the fixed electrode. A weight body is formed on the movable electrode, and is disposed at a position where the center of gravity is shifted. The fixed electrode is composed of three pieces whose surface centroids are not on the same straight line in the electrode plane.
In order to obtain uniform sensitivity and accuracy in all directions, 12
It is desirable to use sector electrodes of the same size arranged at 0 ° intervals.

In the following, a case of a generalized electrode structure as shown in FIG. 1 which is not the same shape and is not arranged at equal intervals will be considered. The figure shows an example in which three electrodes C ₁ , C ₂ and C ₃ , a fixed electrode or a movable electrode are arranged in the same plane. Each electrode capacitance, however, when not considering the misalignment, is represented by the following equation.

[0031]

(Equation 4)

[0032]

(Equation 5)

Here, ε: dielectric constant S _j : area of each electrode do _j : initial electrode distance at the center of gravity of each electrode Ax, Ay, Az: magnitude of acceleration in each axial direction Kz: acceleration in the Z direction Electrode displacement sensitivity Kx _j , Ky _j : Electrode displacement sensitivity to X or Y direction acceleration α _j : Angle when the position of each electrode center is expressed in polar coordinates (positive X axis is 0 °, angle in CCW direction) Cp _j : Stray capacitance

Next, the output voltage when the misalignment and the variation in the CV conversion gain are considered is j,
Assuming that the V conversion gain is Gj and the conversion matrix due to misalignment is Klm (l, m = x, y, z), the following V
The following equation (4), that is, the relational equation of the output voltage of the sensor with respect to the applied acceleration was obtained by rearranging the coefficients when j = 1, 2, and 3, and j = 1.

[0035] _{Vj = G j {εS 1 /} (do 1 + Kz * (K
zxAx + KzyAy + KzzAz) + Kx ₁ (Kxx
Ax + KxyAy + Kxzaz) * cosα _j + Ky _j *
(KxxAx + KyyAy + KyzAz) * sin
α _j ) + Cp _j ｝ (j = 1, 2, 3)

[0036]

(Equation 6)

As a method of obtaining the speed from the output voltage of each electrode, the following equation is obtained by modifying equation (4). _{a j Az + b j Ax +} e j Ay = f j ··· (5) where placed and _{f j = c j / (V} j -d j). ... (6)

To know the acceleration from the output voltage means to solve three ternary linear equations for (Ax, Ay, Az) in equation (5) algebraically. Accordingly, three unknowns can be solved by three equations, and it is understood that three electrodes are sufficient.

The solution of the following simultaneous equations is obtained. a ₁ Az + b ₁ Ax + e ₁ Ay = f ₁ (7) a ₂ Az + b ₂ Ax + e ₂ Ay = f ₂ (8) a ₃ Az + b ₃ Ax + e ₃ Ay = f ₃ (9)

When the solution is obtained from the formulas (7), (8) and (9) (from the formula of the solution) and the formula is returned to the formula of Vj in the formula (6), the following formula is obtained. Ax = ｛(a ₂ b ₃ −a ₃ b ₂ ) (c ₁ / (V ₁ −d ₁ )) + (a ₁ e ₃ −a ₃ e ₁ ) (c ₂ / (V ₂ −d ₂ )) _{+ (a 2 e 1 -a 1} e 2) (c 3 / (V 3 -d 3)) - (a 3 e 2 -a 2 e 3 + a 1 e 3 -a 3 e 1 + a 2 e 1 -a ₁ e ₂ )｝ / D (10) Ay = ｛(a ₂ b ₃ -a ₃ b ₂ ) (c ₁ / (V ₁ -d ₁ )) + (a ₃ b ₁ -a ₁ b ₃₎ ) (C ₂ / (V ₂ −d ₂ )) + (a ₁ b ₂ −a ₂ b ₁ ) (c ₃ / (V ₃ −d ₃ )) − (a ₂ b ₃ −a ₃ b ₂ + a ₃₎ b ₁ −a ₁ b ₃ + a ₁ b ₂ −a ₂ b ₁ )｝ / D (11) Az = ｛(b ₂ e ₃ −b ₃ e ₂ ) (c ₁ / (V ₁ −d _{1) )) + (b 3 e 1} -b 1 e 3) (c 2 / (V 2 -d 2)) + (b 1 e 2 -b 2 e 1) (c 3 / (V 3 -d 3)) − (B ₂ e ₃ −b ₃ e ₂ + b ₃ e ₁ −b ₁ e ₃ + b ₁ e ₂ −b ₂ e ₁ )｝ / D (12)

[0041]

(Equation 7)

In calculating the acceleration, equations (10) and (1)
When the coefficients are put together from 1) and (12), the following equation is obtained.
By predetermining 15 coefficients for each sensor, the output voltage is calculated by the above equation, whereby three-axis acceleration can be obtained.

[0043]

(Equation 8)

In this three-axis acceleration sensor, the position of the movable electrode, that is, the relative position from the initial position including the inclination is uniquely determined with respect to an arbitrary acceleration vector (X, Y, Z-axis acceleration). By detecting the position of the movable electrode, an acceleration is to be obtained. Since the position of the movable electrode can be determined if the distance from three points that are not on a straight line is determined, it can be seen that three electrodes are sufficient as described above.

Therefore, the speed sensor according to the present invention only needs to obtain information that can determine the position of the movable electrode. The means for detecting the relative position from the initial position including the tilt of the movable electrode is based on laser interferometry, a method for detecting the tunnel current from a probe that has come close, or provided on a beam that supports the movable electrode. For example, a method of detecting a change in the piezoelectric material or the piezoresistance may be employed.

When the position of the movable electrode is determined by three points, the centroid of the plane shape of each electrode must not be on the same straight line passing through the center of the Z axis on the XY coordinate system plane. Preferably, as shown in FIG. 3 of the embodiment, the centroid of the planar shape of each electrode is located at a position equally divided into three on the Z-axis center on the XY coordinate system plane. 3
This is the case where the points are arranged at equal intervals as much as possible.
It is desirable to arrange them at 0 ° intervals.

Hereinafter, various configurations of the capacitive acceleration sensor according to the present invention will be described in detail with reference to the drawings. FIG.
As shown in FIG. 3, a metal electrode is formed on one surface of a glass substrate to form a fixed electrode layer 20, which is divided into three equal parts on a circumference of a required radius centered on the Z axis on the XY coordinate system plane. 3 the electrodes are arranged, to form an electrostatic capacitance element C ₁ -C ₃ having the structure disposed facing the three electrode pairs in the Z-axis direction, by processing the silicon substrate in bulk micromachines knee packaging technology 4
The structure of the flexible substrate layer 21 for supporting the movable electrode by this beam was adopted. Further, the weight body 2 is formed under the movable electrode by anodic bonding.
3 to form a capacitance type acceleration sensor having a four-layer structure in which a pedestal layer 22 for securing a moving space for the weight body 23 and a silicon substrate layer 24 serving as an overload stopper are laminated.

In the electrode arrangement shown in FIG. 2, the centroids P _{1 to} P ₃ in the planar shape of the electrodes of the respective capacitance elements C _{1 to} C ₃ are shown.
Reference numeral ₃ denotes a configuration that is not located on the same straight line passing through the center of the Z axis on the XY coordinate system plane, and is located at a position equally divided into three parts around the center of the Z axis.

The fixed electrode layer 20 made of a glass plate disposed on each of the opposing surfaces of the flexible substrate layer 21 is connected to a notch gap provided on the periphery in order to lead outside from the electrode on the opposing surface. An electrode extraction pad 25 on the flexible substrate layer 21
Are provided so that the leads 26 can be connected.

The capacitance type acceleration sensor shown in FIG. 4 has a flexible substrate layer 21 having a weight body 23 formed relatively on the silicon substrate layer 24 serving as a stopper by utilizing the thickness of the silicon substrate. A fixed electrode layer 20 composed of a glass substrate provided with three electrodes 20a and 20b (only two electrodes are shown in the figure) divided into three equal parts on a circumference of a required radius.

The capacitance type acceleration sensor shown in FIG. 5 has a structure in which the three-layer structure of FIG. 4 is made into four layers so that the inside can be sealed. The manufacturing process will be described below. The fixed electrode layer 20 composed of a glass substrate provided with a conical or pyramid-shaped through-hole provided in a required pattern by sandblasting or the like and the semiconductor substrate 30 are anodically bonded at the conical top side of the through-hole. The external electrode 31 and the fixed electrode layer 20 are formed on the entire upper surface.
Are provided with electrodes 20a and 20b in a required pattern. That is, an external electrode 31 can be provided on the entire upper surface of a semiconductor substrate 30 such as a low-resistance B-doped silicon substrate by forming a metal such as Al, Au, or Cu, by vapor deposition or plating. On the side, it can be formed by a technique such as vapor deposition patterning using a metal mask or the like.

Separately, a movable portion 21b formed by providing a support structure with a beam 21a on a semiconductor substrate such as a silicon substrate by a dry or wet etching technique is relatively thick to provide a flexible body having a weight. The substrate layer 21 is manufactured. The fixed electrode layer 20 of the above-mentioned glass composite plate is provided on the flexible substrate layer 21.
Are laminated and anodically bonded. As shown in FIG. 5, the flexible substrate layer 21 is laminated on the silicon substrate layer 24 on which a so-called counterbore is formed, and anodically bonded. At this time, by adjusting the atmosphere at the time of bonding, the gas inside the laminated body is reduced. Can be controlled.

External electrode 31 on the upper surface of the integrated laminate
And a depth corresponding to the thickness of the semiconductor substrate 30, for example, using a dicing saw or the like, as shown in FIG.
Is formed in a required pattern to electrically separate the portion of the semiconductor substrate 30 connected to the counter electrodes 20a and 20b, and the external electrode 31 on the upper surface provided on the separated semiconductor substrate 30 is used to form the counter electrode 20a. , 20b.

The flexible substrate layer 21 in the capacitance type acceleration sensor shown in FIGS. 4 and 5 is made of one semiconductor substrate, but as shown in FIG. When a substrate 21 and a glass substrate 27 are bonded to each other to form a support structure using a beam 21a by an etching technique, the thickness of one semiconductor or one glass substrate may be used as a weight body.

[0055]

In EXAMPLES described above in FIG. 2 and same manufacturing method, the electrode of the variant shown in Figure 7, the centroid P ₁ ~ in the plane shape of the electrode
P ₃ is not on the same straight line passing through the Z axis center onto the X-Y coordinate system plane, and respectively placed in 3 equally divided positions in the Z-axis center 4 having a capacitance element C ₁ -C ₃ A capacitance type acceleration sensor having a layer structure was manufactured.

Using the capacitance type acceleration sensor according to the present invention, the acceleration of gravity when the attitude of the sensor is changed around each axis of the set XYZ coordinate system by the above-described calculation method is calculated. It was measured. 8 to 10 show the relationship between the axis rotation angle and the measured voltage. FIG. 8 shows the X axis rotation, FIG. 9 shows the Y axis rotation,
FIG. 10 shows the Z-axis rotation. In the graph, □ indicates the measured voltage of the capacitance element C ₁ , Δ indicates the measured voltage of the capacitance element C ₂ , and Δ indicates the measured voltage of the capacitance element C ₃ .

The error between the input acceleration calculated value and the measured value was ± 1% or less around each axis. FIG. 11 shows the relationship between the output (acceleration) after the calculation and the shaft rotation angle, and FIG. 12 shows the relationship between the output (acceleration) after the correction calculation and the actual acceleration. The input / output linearity is extremely excellent. Yes,
No effect of the Z-axis acceleration on the x and y output sensitivities is observed at all, and it can be seen that the other-axis sensitivities hardly occur.

[0058]

According to the three-electrode capacitive acceleration sensor of the present invention, the relative position of the movable electrode can be set to any of X, Y,
Since it is uniquely determined with respect to the Z-axis acceleration, the acceleration can be obtained by detecting the position of the movable electrode. The electrode arrangement, the area, and the initial inter-electrode distance can be obtained as long as the prerequisites are maintained. And the alignment error is
It has the advantage of not affecting performance at all.

Therefore, the process selection range is widened, such as adoption of a metal mask method for patterning the fixed electrode during manufacturing and relaxation of alignment accuracy in anodic bonding.
It has the advantage of good manufacturability and low cost. Further, the number of electrodes is smaller than that of the conventional capacitance type, the chip size shrinkage and packaging become easy, and an acceleration sensor having stable performance can be provided at low cost.

In particular, when digital arithmetic is employed in the arithmetic system, the advantage of the conventional method of obtaining X and Y axis outputs as differential outputs with four or five electrodes is eliminated. It is extremely effective to use an acceleration sensor.

[Brief description of the drawings]

FIG. 1 is an XY coordinate explanatory diagram for explaining the operation principle of an acceleration sensor having three electrodes according to the present invention.

FIG. 2 is an explanatory plan view of a glass substrate showing an example of electrode arrangement of the capacitance type acceleration sensor according to the present invention.

FIG. 3 is a vertical sectional view of the capacitance type acceleration sensor according to the present invention.

FIG. 4 is a vertical sectional view showing another configuration of the capacitance type acceleration sensor according to the present invention.

FIG. 5 is a longitudinal sectional view showing another configuration of the capacitance type acceleration sensor according to the present invention.

FIG. 6 is a longitudinal sectional view showing another configuration of the capacitance type acceleration sensor according to the present invention.

FIG. 7 is an explanatory plan view of a glass substrate showing another electrode arrangement example of the capacitance type acceleration sensor according to the present invention.

FIG. 8 is a graph showing a measured voltage of the capacitive acceleration sensor according to the present invention in relation to an X-axis rotation angle.

FIG. 9 is a graph showing a measured voltage of the capacitance type acceleration sensor according to the present invention in relation to a Y-axis rotation angle.

FIG. 10 is a graph showing a measured voltage of the capacitive acceleration sensor according to the present invention in relation to a Z-axis rotation angle.

FIG. 11 is a graph showing the output (acceleration) after calculation based on the measurement of the capacitance type acceleration sensor according to the present invention in relation to the axis rotation angle, where A is the X axis rotation, B is the Y axis rotation, and C is
Indicates the Z-axis rotation. In the graph, the solid line indicates the rotation angle of the X axis, the broken line indicates the Y axis, and the dashed line indicates the rotation angle of the Z axis.

FIG. 12 is a graph showing an output (acceleration) after a correction operation based on the measurement of the capacitance type acceleration sensor according to the present invention in relation to an actual acceleration, where A is the X-axis rotation, B is the Y-axis rotation, C indicates the Z axis rotation.

13A is an explanatory view showing the lower surface of a fixed substrate of the capacitive acceleration sensor, and FIG. 13B is a longitudinal sectional view of the capacitive acceleration sensor.

FIG. 14A is a vertical cross-sectional view of a capacitive acceleration sensor showing a state in which acceleration in the X-axis direction is applied, and FIG. 14B is a longitudinal sectional view of the capacitive acceleration sensor showing a state in which acceleration in the Z-axis direction is applied. FIG.

[Explanation of symbols]

1,2,3,4,5 electrode 10 cylindrical 11 fixed substrate 12 flexible substrate 13 operating element C ₁ -C ₅ capacitive element 20 fixed electrode layer 20a, 20b electrode 21 flexible substrate layer 21a beam 21b movable portion 22 Pedestal layer 23 Weight body 24 Silicon substrate layer 25 Electrode extraction pad 26 Lead 27 Glass substrate 30 Semiconductor substrate 31 External electrode 32 Insulating groove

Claims (10)

[Claims] 1. A sensor having at least one pair of electrodes individually sensitive to three-axis accelerations Ax, Ay, and Az acting on an XYZ rectangular coordinate system defined in advance on a sensor. An acceleration sensor including three pairs of electrodes. 2. The acceleration sensor according to claim 1, wherein the centroid of the planar shape of each electrode is not on the same straight line in the XY coordinate system plane. 3. The acceleration sensor according to claim 1, wherein the centroid of the planar shape of each electrode is divided into three equal parts about the Z axis center on the XY coordinate system plane. 4. The three-electrode pair in the Z-axis direction according to claim 1, wherein three electrodes are arranged on a XY coordinate system plane on a circumference of a required radius centered on the Z-axis and divided into three equal parts. An acceleration sensor having a configuration in which is opposed to each other. 5. A movable body according to claim 1, wherein a weight is provided on the lower surface of the movable portion of the flexible substrate having the support structure by the beam, the upper surface is arranged to face the fixed substrate, and the electrode is arranged on the upper surface of the movable portion. It has a laminated structure of a glass plate and / or a semiconductor substrate having an electrode, and has means for detecting a relative position from an initial position including a tilt of the movable electrode. The acceleration Ax in three axial directions is obtained from the position information of the electrode, An acceleration sensor for determining Ay and Az. 6. The movable body according to claim 1, wherein a weight body is provided on the lower surface of the movable portion of the flexible substrate having the support structure by the beam, the fixed substrate is arranged on the upper surface, and the electrode is arranged on the upper surface of the movable portion. A capacitive acceleration sensor having a laminated structure of a glass plate having electrodes and / or a semiconductor substrate. 7. The fixed electrode layer according to claim 6, wherein three metal electrodes are formed on the lower surface of the glass layer in a required pattern, and the periphery is supported by a beam, and the upper surface has a predetermined gap with respect to the electrode. A movable electrode layer made of silicon, which is arranged to face up and down so as to be movable up and down, and a pedestal layer which supports the periphery of the weight and the movable electrode layer joined by anodic bonding below the movable electrode; A capacitance type acceleration sensor having a four-layer structure including a silicon layer serving as a stopper when a weight joined to an electrode layer abuts upon overload. 8. The fixed electrode layer according to claim 6, wherein metal electrodes are formed on the lower surface of the glass layer in a required pattern for three electrodes, and a supporting structure is provided by patterning on a semiconductor substrate whose periphery is supported by a beam. A flexible substrate layer having a weight body in which the thickness of the movable portion formed is relatively thick, and a glass layer on which the flexible substrate layer is placed and which comes into contact with the weight body when the load is overloaded and serves as a stopper. A capacitance type acceleration sensor having a layer structure. 9. The capacitance type acceleration sensor according to claim 8, wherein the glass layer has a conical or pyramid-shaped through hole provided in a required pattern, and conduction of the metal electrode on the lower surface is performed through the through hole. . 10. A composite board according to claim 8, wherein a glass substrate having a conical or pyramid-shaped through hole provided in a required pattern and a semiconductor substrate are provided in a required pattern on both surfaces of a composite plate joined at the conical top side of the through hole. A capacitance type acceleration sensor in which a composite plate layer in which electrodes are electrically connected to each other via a semiconductor through the through hole is joined to an upper surface of a flexible substrate layer by disposing electrodes so as to face each other and hermetically sealed.