JP2007046927A - Acceleration/angular velocity sensor, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure wiring necessary for detection while maintaining a sealed condition for a weight body. <P>SOLUTION: The weight body 210, a flexible part 220 and a pedestal 230 are formed of a silicon substrate 250, a glass substrate 150 is joined onto an upper face thereof, and a glass substrate 300 is joined onto an under face thereof. A displacement electrode E0 is displaced together with the weight body 210 when the weight body 210 is displaced in response to an acceleration in a sealed space. Fixed electrodes E1-E5 are formed on an under face of the upper substrate 150 to be opposed to the displacement electrode E0, and external electrodes EE1-EE5 are formed on an upper face of the upper substrate 150 to be opposed to the respective fixed electrodes E1-E5. A capacity element is formed of the displacement electrode E0 and the fixed electrodes E1-E5, and another capacity element is formed of the fixed electrodes E1-E5 and the external electrodes EE1-EE5. An electrostatic capacitance value between a terminal T0 and terminals T1-T5 is measured to detect a displacement condition of the weight body 210, and the acting acceleration is detected based thereon. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an acceleration / angular velocity sensor and a method for manufacturing the same, and more particularly to a technique for simplifying wiring in a sensor of a type that detects acceleration and angular velocity using a capacitive element.

  As a small acceleration sensor or an angular velocity sensor (so-called inertial sensor) having a simple structure, a sensor using a capacitive element has been put into practical use. In these types of sensors, normally, a weight body supported so as to be displaceable with a predetermined degree of freedom is prepared, and acceleration and angular velocity acting on the weight body are defined as displacement of the weight body. It has a function to detect. The displacement is detected based on the capacitance value of the capacitive element.

  For example, in Patent Documents 1 to 3 below, a capacitive element is configured by a displacement electrode formed on the weight body side and a fixed electrode formed on the housing body side that accommodates the weight body. An acceleration sensor that can detect the displacement of the weight body based on the change in the capacitance value and electrically detect the applied acceleration is disclosed. By disposing a plurality of capacitive elements, displacement in each coordinate axis direction in the XYZ three-dimensional coordinate system can be detected independently, thus realizing a multidimensional acceleration sensor despite a relatively simple configuration. It becomes possible to do.

Patent Document 4 below discloses a sensor that detects an angular velocity using a substantially similar structure. The angular velocity is detected by supplying an AC signal to a predetermined capacitive element, moving the weight body by the Coulomb force, and generating a Coriolis force generated by the angular velocity acting on the moving weight body. This is performed by detecting the change in the capacitance of the capacitive element. Also by devising and arranging a plurality of capacitive elements, it is possible to cause the weight body to perform repeated movements along a predetermined trajectory such as simple vibration, circular movement, precession movement, etc., and XYZ three-dimensional Since the displacement in the desired coordinate axis direction in the coordinate system can be detected independently, it is possible to realize a multidimensional angular velocity sensor capable of detecting angular velocities around a plurality of coordinate axes in spite of a relatively simple configuration. Become. Further, Patent Document 5 below discloses a three-layer acceleration / angular velocity sensor in which a conductive substrate is sandwiched between two insulating substrates as a sensor having a high mass production effect.
JP-A-4-299227 Japanese Patent Laid-Open No. 5-26754 JP-A-5-215627 JP-A-10-227644 JP 2004-144598 A

  As described above, an acceleration sensor and an angular velocity sensor using a capacitive element have a feature that can detect acceleration and angular velocity of a multidimensional component in spite of a relatively simple configuration. Mass production is performed by using a substrate or the like as a material. However, since the detection of force and the driving of the weight body are performed using the capacitive element, there is no wiring for taking out the capacitance value of the capacitive element to the outside as an electric signal or supplying the driving signal to the capacitive element. Become indispensable. In order to perform wiring with respect to such a capacitive element, it is necessary to form a through hole or a gap for wiring insertion in the wall portion of the room accommodating the weight body.

  On the other hand, it is preferable to keep the chamber containing the weight body as vacuum as possible. This is because the presence of air inside may affect the movement of the weight body. In particular, in the case of an angular velocity sensor, it is necessary to vibrate the weight body at the time of measurement. However, in the atmosphere, it is difficult to stably vibrate the weight body due to the influence of the damping effect due to the viscosity of the air. Therefore, practically, the weight body must be accommodated in a vacuum atmosphere. However, if a wiring through-hole or gap for the capacitive element is formed in the wall portion of the container, it becomes difficult to maintain the inside in a vacuum. This is because sealing with respect to the wiring through-holes or gaps tends to be incomplete and air leakage is likely to occur.

  For example, as disclosed in the above-mentioned Patent Document 5, a sensor having a three-layer structure in which a conductive substrate is sandwiched between two insulating substrates can be mass-produced using a semiconductor manufacturing process. Although there is a merit that it can be reduced, in order to perform physical wiring to the outside, it is necessary to open a through hole in the glass substrate and let the wiring pass. Providing a through hole for such wiring tends to cause air leakage.

  Accordingly, the present invention provides an acceleration / angular velocity sensor capable of securing wiring for a capacitive element necessary for detecting or driving the weight body while maintaining the sealed state of the room containing the weight body. The purpose is to do.

(1) The first aspect of the present invention is due to an external force, a weight body, a container body that accommodates the weight body, a supporting means that supports the weight body in a displaceable form, and an external force. An acceleration / angular velocity sensor having a function of detecting an applied acceleration or angular velocity based on a detection result of the displacement detection unit. ,
The displacement detection means includes a displacement electrode provided on the weight body, a fixed electrode provided at a position facing the displacement electrode on the inner surface of the container, and an external electrode provided at a position facing the fixed electrode on the outer surface of the container. And a detection circuit for detecting acceleration or angular velocity based on the capacitance between the displacement electrode and the external electrode.

(2) According to a second aspect of the present invention, in the acceleration / angular velocity sensor according to the first aspect described above,
A plurality of n displacement electrodes, n fixed electrodes facing each of these displacement electrodes, n external electrodes facing each of these fixed electrodes, each displacement electrode and each corresponding external electrode, And a detection circuit for detecting acceleration or angular velocity based on the capacitance between the two.

(3) A third aspect of the present invention is caused by an external force, a weight body, a container body that accommodates the weight body, a support means that supports the weight body in a displaceable form, and an external force. An acceleration / angular velocity sensor having a function of detecting an applied acceleration or angular velocity based on a detection result of the displacement detection unit. ,
Based on the capacitance between the displacement electrode and the external electrode, the displacement electrode provided on the weight body, the external electrode provided at a position facing the displacement electrode on the outer surface of the container, And a detection circuit for detecting the angular velocity.

(4) According to a fourth aspect of the present invention, in the acceleration / angular velocity sensor according to the third aspect described above,
Acceleration or angular velocity is detected based on the capacitance between a plurality of n displacement electrodes, n external electrodes facing each of these displacement electrodes, and each displacement electrode and each corresponding external electrode. And a detection circuit.

(5) The fifth aspect of the present invention is due to an external force, a weight body, a container body that accommodates the weight body, a support means that supports the weight body in the displaceable form, and an external force. An acceleration / angular velocity sensor having a function of detecting an applied acceleration or angular velocity based on a detection result of the displacement detection unit. ,
Displacement detecting means includes a displacement electrode provided on the weight body, a fixed electrode provided at a position facing the displacement electrode on the inner surface of the container, and an auxiliary electrode provided at a position different from the fixed electrode on the inner surface of the container. Based on the capacitance between the displacement electrode and the external electrode, the wiring part for electrically connecting the fixed electrode and the auxiliary electrode, the external electrode provided at the position facing the auxiliary electrode on the outer surface of the container, and And a detection circuit for detecting acceleration or angular velocity.

(6) According to a sixth aspect of the present invention, in the acceleration / angular velocity sensor according to the fifth aspect described above,
A plurality of n displacement electrodes, n fixed electrodes facing each of these displacement electrodes, n auxiliary electrodes connected to each of these fixed electrodes, and n sheets facing each of these auxiliary electrodes An external electrode and a detection circuit for detecting acceleration or angular velocity based on the electrostatic capacitance between each displacement electrode and each corresponding external electrode are provided.

(7) According to a seventh aspect of the present invention, in the acceleration / angular velocity sensor according to the second, fourth, and sixth aspects described above,
The n displacement electrodes are physically constituted by a single common displacement electrode.

(8) According to an eighth aspect of the present invention, in the acceleration / angular velocity sensor according to the seventh aspect described above,
The weight body is made of a conductive material, and a common displacement electrode is formed by a part of the surface of the weight body.

(9) According to a seventh aspect of the present invention, in the acceleration / angular velocity sensor according to the seventh or eighth aspect described above,
At least a part of the structure composed of the weight body, the support means, and the container is made of a physically continuous conductive material so that a conductive path is formed between the common displacement electrode and at least a part of the container. It is a thing.

(10) According to a tenth aspect of the present invention, in the acceleration / angular velocity sensor according to the ninth aspect described above,
A common external electrode is provided at a predetermined position on the outer surface of the container and facing the equipotential surface of the common displacement electrode via the insulating layer,
The detection circuit detects acceleration or angular velocity based on the capacitance between the common external electrode and each external electrode.

(11) According to an eleventh aspect of the present invention, in the acceleration / angular velocity sensor according to the second, fourth, and sixth aspects described above,
Between the specific external electrode and the corresponding displacement electrode, there is an excitation means for supplying an alternating current signal for excitation having a frequency that matches the physical resonance frequency of the weight body,
The displacement detecting means detects the angular velocity by detecting the displacement caused by the Coriolis force acting as an external force on the weight body in a state where the weight body vibrates due to the supply of the excitation AC signal. It is what I did.

(12) According to a twelfth aspect of the present invention, in the acceleration / angular velocity sensor according to the first to eleventh aspects described above,
The container has a sealed structure, and the inside is maintained in a vacuum.

(13) According to a thirteenth aspect of the present invention, in the acceleration / angular velocity sensor according to the first to twelfth aspects described above,
It has a three-layer structure in which an upper substrate, an intermediate substrate, and a lower substrate are stacked,
A weight body, a flexible portion bonded around the weight body, and a pedestal portion bonded around the flexible portion are formed by the intermediate substrate. A gap is formed between the side of the body and the inner surface of the pedestal,
The lower surface of the upper substrate is bonded to the upper surface of the pedestal portion, and a gap is formed between the upper surface of the weight body and the lower surface of the upper substrate,
A displacement electrode is formed on the upper surface of the weight body, and an external electrode is formed on the upper surface of the upper substrate.
The upper surface of the lower substrate is joined to the lower surface of the pedestal, and a gap is formed between the lower surface of the weight body and the upper surface of the lower substrate.
The upper substrate, the pedestal portion, and the lower substrate constitute a container, and the flexible means constitutes the support means.

(14) According to a fourteenth aspect of the present invention, in the acceleration / angular velocity sensor according to the thirteenth aspect described above,
The intermediate substrate is made of a conductive material, and the detection circuit is wired to the displacement electrode via the pedestal.

(15) According to a fifteenth aspect of the present invention, in the acceleration / angular velocity sensor according to the thirteenth or fourteenth aspect described above,
A groove for forming a thin portion having a small thickness is dug in the upper surface of the upper substrate, and an external electrode is formed on the bottom surface of the groove.

(16) According to a sixteenth aspect of the present invention, in the acceleration / angular velocity sensor according to the fifteenth aspect described above,
The groove in which the external electrode is formed is filled with a reinforcing material.

(17) According to a seventeenth aspect of the present invention, in the acceleration / angular velocity sensor according to the first to sixteenth aspects described above,
In order to detect the capacitance between the displacement electrode and the external electrode,
An AC power supply that supplies an AC signal for detection having a frequency that does not match the physical resonance frequency of the weight body to one electrode;
A detection circuit for detecting an amplitude component of an AC signal generated at the other electrode;
Is provided in the detection circuit.

(18) According to an eighteenth aspect of the present invention, in the acceleration / angular velocity sensor according to the first to sixteenth aspects described above,
In order to detect the capacitance between the displacement electrode and the external electrode,
A potential fixing means for fixing the potential of one of the electrodes;
An AC power supply for supplying an AC signal for detection having a frequency not matching the physical resonance frequency of the weight body to the other electrode via a resistance element;
Phase detection means for detecting the phase of the AC signal generated on the other electrode;
Is provided in the detection circuit.

(19) According to a nineteenth aspect of the present invention, in the manufacturing method for manufacturing the acceleration / angular velocity sensor according to the thirteenth aspect,
Forming a through-hole penetrating front and back at a predetermined location of the silicon substrate;
Bonding an insulating substrate to the lower surface of the silicon substrate;
Polishing the lower surface of the insulating substrate until a predetermined thickness is obtained;
Forming an insulating film on the upper surface of the silicon substrate;
Forming a conductive layer in the groove formed by the upper surface of the insulating film and the through hole; and
Patterning the conductive layer to form an external electrode located at the bottom of the groove and a wiring for the external electrode;
Thus, an upper substrate having a two-layer structure of a silicon substrate and an insulating substrate and having external electrodes formed thereon is manufactured.

(20) According to a twentieth aspect of the present invention, in the method for manufacturing an acceleration / angular velocity sensor according to the nineteenth aspect described above,
After patterning the conductive layer, a step of filling the groove with a reinforcing material is further performed.

(21) According to a twenty-first aspect of the present invention, in the method for manufacturing an acceleration / angular velocity sensor according to the nineteenth or twentieth aspect described above,
The step of forming a through-hole in the silicon substrate is performed by anisotropic etching so that a tapered through-hole that extends upward is formed,
Prepare a glass substrate as an insulating substrate, and perform anodic bonding between the silicon substrate and the glass substrate,
The step of forming the insulating film on the upper surface of the silicon substrate is performed by forming an insulating film made of silicon oxide by oxidizing the silicon surface.

  In the acceleration / angular velocity sensor according to the present invention, signals for detecting the displacement of the weight body and driving the weight body are exchanged using the capacitive coupling of the external electrode formed outside the container. It becomes possible to secure the wiring necessary for detection while maintaining the sealed state of the weight body.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

<<< §1. Conventional acceleration sensor >>>
The present invention relates to a device for inputting and outputting signals with respect to a conventional acceleration sensor or angular velocity sensor using a capacitive element. Therefore, here, the structure and operation of a general conventional acceleration sensor using a capacitive element will be briefly described.

  FIG. 1 is a side sectional view showing an example of the structure of a conventional acceleration sensor. The illustrated acceleration sensor has a structure in which three substrates, an upper substrate 100, an intermediate substrate 200, and a lower substrate 300 are laminated. Each substrate is made of an insulating material. Each of the upper substrate 100 and the lower substrate 300 is a simple flat substrate, but the intermediate substrate 200 is composed of three parts, a weight body 210, a flexible portion 220, and a pedestal portion 230, as shown in the figure. Yes. The flexible portion 220 is a portion having flexibility because it is thin as shown in the figure, and is joined around the weight body 210. The periphery of the flexible portion 220 is joined to the pedestal portion 230. The pedestal portion 230 is a structure that forms an outer wall that surrounds the periphery of the flexible portion 220. The upper substrate 100 is bonded to the upper surface of the pedestal portion 230, and the lower substrate 300 is bonded to the lower surface of the pedestal portion 230.

  A space S1 is formed between the upper surface of the weight body 210 and the lower surface of the upper substrate 100, and a space S2 is formed between the side surface of the weight body 210 and the inner surface of the pedestal portion 230. A gap S <b> 3 is formed between the bottom surface of the weight body 210 and the upper surface of the lower substrate 300. In addition, the pedestal 230, the upper substrate 100, and the lower substrate 300 constitute a housing that houses the weight body 210 therein. Eventually, the weight body 210 is supported in such a manner that it can be displaced with a predetermined degree of freedom inside the container. The flexible part 220 functions as a support means for supporting the weight body 210 in a displaceable manner. That is, the weight body 210 is displaced inside the housing body when the flexible portion 220 is bent.

  Here, for convenience of explanation, as shown in the figure, the origin of the XYZ three-dimensional coordinate system is taken at the position of the center of gravity G of the weight body 210, the X axis is in the right direction of the figure, the Z axis is in the upward direction of the figure, The Y axis is defined in the vertical direction. The side sectional view of FIG. 1 corresponds to a section obtained by cutting the sensor along the XZ plane, and the upper substrate 100 and the lower substrate 300 are substrates whose upper and lower surfaces are parallel to the XY plane.

  The basic principle of this acceleration sensor is that when the weight body 210 is displaced inside the container due to the action of an external force caused by acceleration, this displacement is detected as a change in the capacitance value of the capacitive element. is there. Therefore, as shown in FIG. 1, a total of five sets of capacitive elements are formed by the fixed electrodes E1 to E5 formed on the lower surface of the upper substrate 100 and the displacement electrodes E6 to E10 formed on the upper surface of the weight body 210. (Only the electrodes located on the XZ plane appear in FIG. 1).

  FIG. 2 is a bottom view of the upper substrate 100 of the sensor shown in FIG. As illustrated, five fixed electrodes E1 to E5 are formed on the lower surface of the upper substrate 100. These fixed electrodes E1 to E5 are not affected by the displacement of the weight body 210 and are fixed to the inner surface of the container. On the other hand, FIG. 3 is a top view of the intermediate substrate 200 of the sensor shown in FIG. As shown in the figure, five displacement electrodes E6 to E10 are formed on the upper surface of the weight body 210 indicated by a broken line. These displacement electrodes E6 to E10 are displaced together with the weight body 210. Here, each fixed electrode E1-E5 and each displacement electrode E6-E10 are arrange | positioned in the position which opposes, respectively, and each counter electrode is mutually equal in shape and magnitude | size. The electrodes E1, E2, E6, E7 are symmetric with respect to the XZ plane, the electrodes E3, E4, E8, E9 are symmetric with respect to the YZ plane, and the electrodes E5, E10 are symmetric with respect to both the XZ plane and the YZ plane. It has become.

  Here, the capacitive element formed by the counter electrodes E1 and E6 is called C1, the capacitive element formed by the counter electrodes E2 and E7 is called C2, and the capacitive element formed by the counter electrodes E3 and E8 is called C3. The capacitive element formed by the counter electrodes E4 and E9 is referred to as C4, and the capacitive element formed by the counter electrodes E5 and E10 is referred to as C5. The capacitive element C1 is disposed on the X axis positive area, the capacitive element C2 is disposed on the X axis negative area, the capacitive element C3 is disposed on the Y axis positive area, and the capacitive element C4 is disposed on the Y axis negative area. Arranged on the region, the capacitive element C5 is arranged on the Z-axis.

  Since the operation of the acceleration sensor using such a capacitive element is described in detail in the above-mentioned patent documents and the like, only a simple operation principle will be described here. In FIG. 1, when a force in the positive direction of the X axis acts on the center of gravity G due to acceleration, the weight body 210 is displaced in the right direction in the drawing by the bending of the flexible portion 220. As a result, the distance between the electrodes of the capacitive element C1 is narrowed and the distance between the electrodes of the capacitive element C2 is widened. Therefore, by detecting the difference between the capacitance values of both capacitive elements, the X-axis direction component of the applied acceleration Can be requested. When the direction of acceleration is reversed, the sign of the difference in capacitance value is reversed. Similarly, the Y-axis direction component of the applied acceleration can be detected as a difference between the capacitance value of the capacitive element C3 and the capacitance value of the capacitive element C4.

  When acceleration in the Z-axis direction is applied, a force in the vertical direction in the figure is applied to the weight body 210, and the weight body 210 is displaced in the vertical direction in the figure. For this reason, the electrode interval of the capacitive element C5 varies. Therefore, the Z-axis direction component of the applied acceleration can be detected by increasing or decreasing the capacitance value of the capacitive element C5.

  Although the principle of acceleration detection by this conventional acceleration sensor has been briefly described above, since such a sensor detects the displacement of the weight body 210 using a capacitive element, the electrostatic capacitance of each capacitive element. Wiring for extracting the value to the outside as an electrical signal is indispensable. FIG. 4 is a sectional side view of a conventional acceleration sensor provided with this wiring. The sensor shown in FIG. 4 is slightly different in structure from the sensor shown in FIG. 1 in consideration of the convenience of wiring.

  That is, in the sensor shown in FIG. 4, a single physical common displacement electrode E0 is formed on the upper surface of the weight body 210 instead of the displacement electrodes E6 to E10 in the sensor shown in FIG. Further, the weight body 210, the flexible portion 220, and the pedestal portion 230 are made of a conductive material. Therefore, to distinguish from the intermediate substrate 200 made of an insulating material in the sensor shown in FIG. 1, the intermediate substrate of the sensor shown in FIG. FIG. 5 is a top view of the intermediate substrate 250, and the shape of the common displacement electrode E0 formed on the top surface of the weight body 210 is clearly shown.

  The common displacement electrode E0 shown in FIG. 5 functions as a substitute for the five displacement electrodes E6 to E10 shown in FIG. Since the fixed electrodes E1 to E5 formed on the lower surface of the upper substrate 100 are individual electrodes that are physically independent of each other, the displacement electrode side facing these is physically single as shown in FIG. Even if one common displacement electrode E0 is used, no problem occurs in the operation of the sensor.

  Thus, if the displacement electrode side is constituted by the common displacement electrode E0, the upper surface of the weight body 210 is not necessarily made of an insulating material. Therefore, the intermediate substrate can be constituted by the intermediate substrate 250 made of a conductive material. it can. In addition, if the intermediate substrate 250 is a conductive material, the entire intermediate substrate 250 has the same potential as the common displacement electrode E0, and therefore wiring to the outside with respect to the common displacement electrode E0 is extremely simple. That is, when external wiring is performed on any part of the intermediate substrate 250, wiring to the common displacement electrode E0 is completed. FIG. 4 shows a state where the connection terminal T0 is connected to the outer surface of the pedestal 230. In general, the connection terminal T0 may be used while being grounded.

  On the other hand, it is necessary to individually wire the five fixed electrodes E1 to E5 formed on the lower surface of the upper substrate 100. In FIG. 4, in order to perform wiring for the three fixed electrodes E1, E2, and E5, a through hole is formed in the upper substrate 100, and the wiring portions L1, L2, and L5 are inserted into the through hole and fixed. An example is shown in which the electrodes E1, E2, E5 are electrically connected to external connection terminals T1, T2, T5.

  However, as described above, when wiring to each capacitor element is performed by such a method, there is a problem that the sealed state inside the container tends to be incomplete. For example, in the case of the illustrated example, air leakage is likely to occur through the through holes for inserting the wiring portions L1, L2, and L5. As described above, the problem of incomplete sealing of the wiring portion is inevitable as long as the wiring inside the container is wired to the outside.

  On the other hand, as described above, it is preferable to keep the chamber containing the weight body 210 as vacuum as possible. In the case of the example shown in FIG. 4, if air exists in the gaps S1, S2, and S3, the movement of the weight body is unfavorably affected by the damping effect due to the viscosity of the air. The example shown here is an example of an acceleration sensor, but in the case of an angular velocity sensor, it is necessary to vibrate the weight body at the time of measurement, so it is practically necessary to house the weight body in a vacuum atmosphere. It is essential. However, if the sealed state of the container is insufficient due to the wiring structure to the outside, it is difficult to maintain the inside in a vacuum.

  The present invention proposes a novel device for solving such a problem of the conventional sensor, and detects the displacement of the weight body while maintaining the sealed state of the room containing the weight body. Therefore, it is possible to secure signal wiring necessary for the operation.

<<< §2. Basic embodiment of the present invention >>
FIG. 6 shows a side sectional view of the acceleration sensor according to the basic embodiment of the present invention. The acceleration sensor shown in FIG. 6 is obtained by replacing the upper substrate 100 of the conventional sensor shown in FIG. 4 with an upper substrate 150. The intermediate substrate 250 and the lower substrate 300 are the same as those shown in FIG. Is exactly the same. Further, the bottom view of the upper substrate 150 is completely the same as the bottom view of the upper substrate 100 shown in FIG. 2, and five fixed electrodes E1 to E5 are formed.

  Compared with the upper substrate 100 shown in FIG. 4, the upper substrate 150 shown in FIG. 6 has the following two features. The first feature is that the upper substrate 150 is composed of a thick portion 151 at the peripheral portion and a thin portion 152 surrounded by the thick portion 151, and a difference in thickness results in a difference in level. A groove H1 is formed above the portion 152. The second feature is that five external electrodes EE1 to EE5 are formed on the bottom surface of the groove portion H1 (that is, the upper surface of the thin portion 152).

  These features are clearly shown in the top view of the upper substrate 150 shown in FIG. When the plan view of the external electrodes EE1 to EE5 shown in FIG. 7 is compared with the fixed electrodes E1 to E5 shown in FIG. 2, electrodes having the same shape and the same size sandwich the thin portion 152. You can see that they are facing each other. That is, the external electrode EE1 having the same shape and size is opposed above the fixed electrode E1, and the external electrode EE2 having the same shape and size is opposed above the fixed electrode E2. The same applies hereinafter. Here, the capacitive element formed by the counter electrodes E1 and EE1 is called CC1, the capacitive element formed by the counter electrodes E2 and EE2 is called CC2, and the capacitive element formed by the counter electrodes E3 and EE3 is called CC3. The capacitive element formed by the counter electrodes E4 and EE4 is called CC4, and the capacitive element formed by the counter electrodes E5 and EE5 is called CC5.

  As shown in FIG. 6, the five external electrodes EE1 to EE5 formed on the upper surface of the upper substrate 150 are connected to the connection terminals T1 to T5. The five external electrodes EE1 to EE5 are formed on the outer surface of the sensor housing (the upper body 150, the pedestal 230, the lower board 300, and the structure that forms the chamber for housing the weight body 210). Therefore, even if the wiring for connecting the external electrodes EE1 to EE5 and the connection terminals T1 to T5 is provided, there is no problem in the sealed state of the container. As described above, since the intermediate substrate 250 is made of a conductive material, if the wiring from the connection terminal T0 is connected to the outer surface of the pedestal portion 230 as shown, the gap between the common displacement electrode E0 and the connection terminal T0. Wiring can be secured without any problem.

  As described above, in the sensor shown in FIG. 6, no physical wiring is performed to the outside with respect to the common displacement electrode E0 and the fixed electrodes E1 to E5 existing inside the container. Thus, the structure which eliminated all the wiring which connects the inside and the exterior of a container is effective in improving the sealing property of a container. Actually, the intermediate substrate 250 is formed of a silicon substrate, the upper substrate 150 and the lower substrate 300 are formed of a glass substrate, and the upper surface of the pedestal portion 230 is bonded to the lower surface of the upper substrate 150 and the lower surface of the pedestal portion 230 and the lower substrate 300 If the upper surface of the container is bonded using an anodic bonding method, the inside of the container can be made into a completely sealed space. If this anodic bonding is performed in a vacuum chamber, the inside of the container can be maintained in a vacuum, and the weight body 210 can be confined in a vacuum atmosphere.

  Of course, the basic principle of the acceleration detection in the sensor shown in FIG. 6 is the same as the principle of the sensor shown in FIG. 4, and five sets of capacitive elements C1 to C5 constituted by the common displacement electrode E0 and the fixed electrodes E1 to E5. The change in the capacitance of C5 is detected as an electric signal. However, in the case of the sensor shown in FIG. 6, instead of directly measuring the capacitance values of the capacitance elements C1 to C5, the capacitance elements CC1 to CC5 newly generated by forming the external electrodes EE1 to EE5. The value taking into account the capacitance will be measured. Since the capacitances of the capacitive elements C1 to C5 vary depending on the displacement of the weight body 210, they are referred to as variable capacitive elements here. On the other hand, the capacitances of the capacitive elements CC1 to CC5 are constant regardless of the displacement of the weight body 210. Here, these are called auxiliary capacitance elements.

  FIG. 8A is a partial cross-sectional side view showing extracted portions of each electrode in order to explain the operation of the acceleration sensor shown in FIG. In addition, since this figure has shown the cross section which cut | disconnected the sensor by XZ plane, fixed electrode E3, E4 and external electrode EE3, EE4 do not appear in a figure. As shown in the figure, five fixed electrodes E1 to E5 are arranged so as to face above the common displacement electrode E0, and five external electrodes EE1 to EE5 are arranged so as to face each other above them. Has been. When the inside of the container is evacuated, the space between the common displacement electrode E0 and the fixed electrodes E1 to E5 is maintained in a vacuum, but between the fixed electrodes E1 to E5 and the external electrodes EE1 to EE5, A thin portion 152 is interposed.

  FIG. 8 (b) is an equivalent circuit diagram of FIG. 8 (a). Assuming that the fixed electrodes E1 to E5 have a function as an upper electrode for the variable capacitance elements C1 to C5 and a function as a lower electrode for the auxiliary capacitance elements CC1 to CC5, as illustrated, Between the connection terminal T0 and the connection terminals T1 to T5, variable capacitance elements C1 to C5 and auxiliary capacitance elements CC1 to CC5 are connected in series, respectively. Therefore, the capacitance value between the connection terminal T0 and each of the connection terminals T1 to T5 is a capacitance value when two capacitance elements are connected in series. For example, if the capacitance value of the capacitive element C1 is represented by the same symbol C1, and the capacitance value of the capacitive element CC1 is represented by the same symbol CC1, the capacitance value between the connection terminals T0 / T1 is 1 / (1 / C1 + 1 / CC1). Here, since the capacitance value of the auxiliary capacitance element CC1 is always constant, the variation in the capacitance value between the connection terminals T0 / T1 indicates the variation in the capacitance value of the variable capacitance element C1. .

  As a result, also in the acceleration sensor shown in FIG. 6, it is possible to detect each coordinate axis direction component of the applied acceleration in the XYZ three-dimensional coordinate system by the same method as the conventional sensor described in Section 1. For example, the X-axis direction component can be obtained as a difference between the capacitance value between the connection terminals T0 / T1 and the capacitance value between the connection terminals T0 / T2. In FIG. 8B, the arrows of the variable capacitance elements C1 and C2 are reversed in order to show that such differential detection is performed. Similarly, the Y-axis direction component is not shown in FIG. 8, but is obtained as a difference between the capacitance value between the connection terminals T0 / T3 and the capacitance value between the connection terminals T0 / T4. Can do. The Z-axis direction component can be obtained by increasing or decreasing the capacitance value between the connection terminals T0 / T5 (by increasing or decreasing from the reference value).

  Of course, the acceleration sensor shown in FIG. 6 shows one embodiment of the present invention, and the sensor according to the present invention is not limited to such a structure. Further, as described in detail in Section 7, the present invention is not limited to the acceleration sensor, but can be applied to an angular velocity sensor. In short, the present invention includes a weight body 210, a housing body that accommodates the weight body 210 (in the case of FIG. 6, the upper substrate 150, the pedestal portion 230, the lower substrate 300), and the weight body in the housing body. Support means for supporting in a displaceable manner (in the case of the example of FIG. 6, the flexible portion 220) and displacement detection means for detecting the displacement of the weight body with respect to the container due to external force (of FIG. 6) In the case of an example, each electrode and a detection circuit to be described later are provided, and can be widely applied to sensors having a function of detecting an applied acceleration or angular velocity based on a detection result of the displacement detection means.

  The essential point of the basic embodiment described here is that a common displacement electrode E0 (an individual displacement electrode E6 to E10 is provided as in the example shown in FIG. 3) provided on the weight body 210 as an electrode constituting the displacement detection means. The fixed electrodes E1 to E5 provided at positions facing the common displacement electrode E0 on the inner surface of the container, and the external electrodes EE1 to EE5 provided at positions facing the fixed electrodes E1 to E5 on the outer surface of the container. And the acceleration or angular velocity is detected based on the capacitance between the common displacement electrode E0 and the external electrodes EE1 to EE5.

  By adopting such a configuration, in the sensor according to the present invention, it is possible to eliminate any wiring connecting the inside and the outside of the container, and it is possible to improve the sealing property of the container. In other words, it is possible to secure wiring necessary for detection while maintaining the sealed state of the weight body.

<<< §3. Detection circuit used in the present invention >>
In §2 described above, the structure and operating principle of the acceleration sensor shown in FIG. 6 have been described. The acceleration sensor shown in FIG. 6 is actually a structure that should be referred to as a sensor body, and in order to actually detect acceleration, it is necessary to connect a dedicated detection circuit to this structure. That is, the original acceleration sensor should be configured by adding a detection circuit as described later to the sensor body shown in FIG. However, in this specification, the sensor main body shown in FIG. 6 is also referred to as an acceleration sensor unless it is particularly necessary to make a distinction.

  The detection circuit used together with the acceleration sensor shown in FIG. 6 may be any circuit as long as it has a function of detecting a capacitance value at a predetermined location or a difference between them. Now, a specific detection circuit will be exemplified.

  FIG. 9 is a circuit diagram showing an example of such a detection circuit. In this circuit diagram, E0 is the common displacement electrode E0 shown in FIG. 6, E1 to E5 are the fixed electrodes E1 to E5 shown in FIG. 6, and EE1 to EE5 are the external electrodes EE1 to EE5 shown in FIG. is there. As described above, the variable capacitors C1 to C5 and the auxiliary capacitors CC1 to CC5 are formed by these electrodes as shown in the drawing. In this example, the capacitance values of the auxiliary capacitance elements CC1 and CC2 are equal to each other, and the capacitance values of the auxiliary capacitance elements CC3 and CC4 are also set to be equal to each other. Further, in a state where the weight body is not displaced, the capacitance values of the capacitive elements C1 and C2 are set to be equal to each other, and the capacitance values of the capacitive elements C3 and C4 are also set to be equal to each other. Setting the capacitance values to be equal in this way is a consideration for facilitating later signal processing, and it is not always necessary to set the capacitance values equally. On the other hand, T0 to T5 in this circuit diagram correspond to the connection terminals T0 to T5 shown in FIG. In the end, the capacitive elements C1 to C5 and CC1 to CC5 in the circuit diagram shown in FIG. 9 show the structure of the acceleration sensor shown in FIG. 6, and the actual detection circuit has the other configuration shown in FIG. That is, it is constituted by an AC power source 400, difference circuits 410 and 420, and detection circuits 430, 440, and 450. This detection circuit is electrically connected to the structure of the acceleration sensor shown in FIG. 6 via connection terminals T0 to T5.

  The AC power supply 400 has a function of supplying a predetermined AC signal for detection to the connection terminal T0. As is apparent from the acceleration sensor of FIG. 6, the AC signal for detection supplied from the AC power source 400 passes through the pedestal portion 230, the flexible portion 220, and the weight body 210 from the connection terminal T0, and the common displacement electrode E0. Added to. Since one end of the AC power supply 400 is grounded, the potential of the common displacement electrode E0 alternately takes positive and negative potentials with respect to the ground potential.

  FIG. 10 is a signal waveform diagram for explaining the operation of the detection circuit shown in FIG. Assuming that the potential of the connection terminal T0 is the voltage V0, the voltage V0 becomes an AC signal that swings up and down with reference to the ground potential 0 as shown in FIG. When such an AC signal is applied to the common displacement electrode E0, potential fluctuations according to the voltage V0 occur in the fixed electrodes E1 to E5 that are AC-coupled to the common displacement electrode E0. The potential fluctuations corresponding to the voltage V0 also occur in the external electrodes EE1 to EE5 that are AC-coupled to the fixed electrodes E1 to E5, respectively.

  Here, as shown in the circuit diagram of FIG. 9, the potentials of the connection terminals T1 to T5 (that is, the potentials of the external electrodes EE1 to EE5) are referred to as voltages V1 to V5, respectively. The AC signal (voltage V0) supplied to the connection terminal T0 is transmitted as an AC signal (voltages V1 to V5) to the connection terminals T1 to T5 through AC coupling by the capacitive elements. Therefore, the voltages V1 to V5 are AC signals having the same cycle as the voltage V0. This is why the voltages V1 and V2 shown in FIG. 10 are signals synchronized with the voltage V0. Actually, the waveforms of the voltages V1 and V2 cause a slight phase difference and a rounded waveform as compared with the waveform of the voltage V0. Here, the phase difference and the rounded waveform are ignored. Give an explanation.

  Now, comparing the signals of the voltages V1 and V2 shown in FIG. 10 with the signal of the voltage V0, it can be seen that the frequencies are the same but the amplitudes are different. This is because, when an AC signal supplied to the common displacement electrode E0 is transmitted to the external electrodes EE1 to EE5 through each capacitive element, the amplitude of the signal is determined depending on the degree of AC coupling of each capacitive element. Because.

  FIG. 10 is obtained when the force in the right direction (X-axis positive direction) acts on the weight body 210 in the acceleration sensor shown in FIG. 6 and the weight body 210 is displaced in the right direction. It shows a signal waveform to be generated. In this case, the distance between the electrodes E0 / E1 is reduced, the capacitance value of the variable capacitance element C1 is increased (the degree of AC coupling is increased), and conversely, the distance between the electrodes E0 / E2 is increased. The capacitance value of the variable capacitance element C2 decreases (the degree of AC coupling decreases). As a result, when the amplitude of the voltage V1 is compared with the amplitude of the voltage V2, the former is larger than the latter. Therefore, the difference V1−V2 between the two voltages is an amount related to the amount of displacement of the weight body 210 in the X-axis direction.

  The difference circuit 410 in the circuit diagram shown in FIG. 9 is a circuit that outputs this voltage difference V1-V2. The signal waveform indicating the voltage difference V 1 −V 2 shown in FIG. 10 is a signal output from the difference circuit 410. The detection circuit 430 connected to the subsequent stage of the difference circuit 410 detects the output signal (voltage V1-V2) of the difference circuit 410 by using the voltage V0 as a detection signal, as shown in FIG. It is a circuit that outputs a voltage Vx. This voltage Vx is output to the output terminal Tx. After all, the detection circuit 430 functions to output the signal component included in the signal wave of the voltage V1-V2 as the voltage Vx when the AC signal of the voltage V0 is a carrier wave. In other words, the detection circuit 430 outputs the ratio of “the voltage V1−V2 given as the input signal” to the “voltage V0 given as the detection signal” as an absolute value of the voltage, and as described later, Is output as the polarity of the voltage. Such a detection circuit 430 is a circuit widely used in the field of angular velocity sensors and the like, and detailed description of the circuit is omitted here.

  As described above, in the acceleration sensor shown in FIG. 6, the more the weight body 210 is displaced in the X-axis positive direction, the larger the difference between the voltage V1 and the voltage V2, and the larger the amplitude of the voltage V1-V2. The voltage Vx also increases. Conversely, when the weight body 210 is displaced in the negative direction of the X axis, the difference between the voltage V1 and the voltage V2 increases as the displacement is increased. However, the sign of the voltage V1-V2 is reversed.

  FIG. 11 is obtained when the force in the left direction (X-axis negative direction) acts on the weight body 210 and the weight body 210 is displaced in the left direction in the acceleration sensor shown in FIG. It shows a signal waveform to be generated. In this case, the distance between the electrodes E0 / E1 is increased, the capacitance value of the variable capacitance element C1 is decreased (the degree of AC coupling is reduced), and conversely, the distance between the electrodes E0 / E2 is narrow. Thus, the capacitance value of the variable capacitance element C2 increases (the degree of AC coupling increases). As a result, when comparing the amplitude of the voltage V1 and the amplitude of the voltage V2, the latter is larger than the former. Therefore, the voltage V1-V2 shown in FIG. 11 has the sign reversed from that of the voltage V1-V2 shown in FIG. 10, and the sign of the voltage Vx shown in FIG. 11 is negative. As described above, the detection circuit 430 outputs a positive voltage if the “voltage V0 given as the detection signal” and the “voltage V1-V2 given as the input signal” have the same phase, and may have an opposite phase. A function of outputting a negative voltage.

  As a result, in the circuit shown in FIG. 9, the voltage Vx output to the output terminal Tx indicates the direction and magnitude of the X-axis direction component of acceleration. That is, if the voltage Vx is positive, the force applied due to the acceleration is in the positive direction of the X axis, and if the voltage Vx is negative, it is in the negative direction of the X axis. The absolute value of indicates the magnitude of acceleration. In exactly the same manner, a voltage Vy indicating the direction and magnitude of the Y-axis direction component of acceleration is output to the output terminal Ty. Further, a voltage Vz indicating the direction and magnitude of the Z-axis direction component of acceleration is output to the output terminal Tz. Since the voltage Vz is not obtained based on the difference between the two voltages, the sign cannot indicate the direction of the Z-axis direction component of the applied acceleration, but the predetermined reference value (acceleration Z The direction of the Z-axis direction component can be indicated by whether it is larger or smaller than the value of the voltage Vz obtained when the axial direction component is 0), and the magnitude of the Z-axis direction component is determined by the distance from the reference value. Can be shown.

  Note that the detection AC signal supplied from the AC power supply 400 is preferably a signal having a frequency that does not match the physical resonance frequency of the weight body 210 as much as possible. This is because if a signal having a frequency that matches the physical resonance frequency of the weight body 210 is supplied, vibration may be induced in the weight body 210 due to the Coulomb force acting between the electrodes. (As described in §7, when used as an angular velocity sensor, such vibration is positively induced). In the case of a general sensor structure having a structure as shown in FIG. 6, the physical resonance frequency of the weight body 210 is about 4 to 20 kHz. Thus, for example, if a signal of about 200 to 500 kHz is used as the detection AC signal supplied from the AC power supply 400, vibration induction on the weight body 210 can be avoided.

  After all, the principle of the detection circuit shown in FIG. 9 is that one electrode (in this case, the common displacement electrode E0) is used to detect the capacitance between the common displacement electrode E0 and each of the external electrodes EE1 to EE5. ) Is supplied with a detection AC signal having a frequency that does not match the physical resonance frequency of the weight body 210, and at this time, the other electrode (in this example, each external electrode EE1 to EE5) is supplied. This means that the amplitude component of the generated AC signal is detected. This utilizes the phenomenon that when the electrode spacing of each of the variable capacitance elements C1 to C5 changes, the degree of AC coupling changes and the amplitude component of the transmitted AC signal changes.

  On the other hand, the detection circuit shown in FIG. 12 is based on the principle of recognizing the change in the electrode spacing of each of the variable capacitance elements C1 to C5 based on the change in the phase of the detection AC signal and detecting the applied acceleration. Circuit. Here, only components for detecting the X-axis direction component of the applied acceleration are shown. The variable capacitive elements C1 and C2 and the auxiliary capacitive elements CC1 and CC2 shown in FIG. 12 are capacitive elements configured by the electrodes in the acceleration sensor shown in FIG. 6, and as described above, the capacitive elements C1 and CC1 are connected in series. The capacitive elements C2 and CC2 are connected in series. Here, the capacitance values of the capacitive elements CC1 and CC2 are equal to each other, and when the weight body is not displaced, the capacitance values of the capacitive elements C1 and C2 are set to be equal to each other. Subsequent signal processing becomes easy, but such setting is not essential.

  Here, the lower electrodes (common displacement electrode E0) of the variable capacitance elements C1 and C2 are grounded, and the upper electrodes (external electrodes EE1 and EE2) of the auxiliary capacitance elements CC1 and CC2 have resistance values. The rectangular wave signals φ1 and φ2 having the same period and different phases are applied through the equal resistance elements R1 and R2. At this time, the rectangular wave signal appearing at the upper electrodes (external electrodes EE1, EE2) of the auxiliary capacitance elements CC1, CC2 is input to the EX-OR circuit 460, and a signal corresponding to the exclusive OR of the two rectangular wave signals is obtained. It is output to the output terminal TTx.

  The output signal of the EX-OR circuit 460 in this circuit is a signal indicating the phase difference between the rectangular wave signals appearing on the electrodes (external electrodes EE1, EE2) above the auxiliary capacitance elements CC1, CC2. That is, a rectangular wave having a duty ratio corresponding to the phase difference between both signals is obtained. Since the phase difference between both signals is an amount corresponding to the difference between the capacitance value of the variable capacitance element C1 and the capacitance value of the variable capacitance element C2, the duty ratio of the rectangular wave obtained at the output terminal TTx is: The X-axis direction component of the applied acceleration is shown. The detection circuit for the Y-axis direction component can also be realized by a similar configuration.

  On the other hand, the detection circuit shown in FIG. 13 is a circuit for detecting the Z-axis direction component. Here, the variable capacitive element C5 and the auxiliary capacitive element CC5 are capacitive elements constituted by electrodes in the acceleration sensor shown in FIG. 6, and as described above, both capacitive elements are connected in series. On the other hand, the fixed capacitance element C0 is a capacitance element prepared separately from the acceleration sensor shown in FIG. 6, and the capacitance value functions as a reference value.

  As shown in the drawing, the lower electrode (common displacement electrode E0) of the variable capacitor C5 and the lower electrode of the fixed capacitor C0 are grounded, and the upper electrode (external electrode EE5) and the fixed capacitor of the auxiliary capacitor CC5. Rectangular wave signals φ1 and φ2 are applied to the electrodes above the element C0 via resistance elements R3 and R4, respectively. At this time, the rectangular wave signal appearing at the upper electrode (external electrode EE5) of the auxiliary capacitive element CC5 and the upper electrode of the fixed capacitive element C0 is input to the EX-OR circuit 470, and the exclusive OR of both rectangular wave signals is input. Is output to the output terminal TTz.

  The output signal of the EX-OR circuit 470 in this circuit indicates the phase difference between the rectangular wave signal appearing at the upper electrode (external electrode EE5) of the auxiliary capacitive element CC5 and the rectangular wave signal appearing at the upper electrode of the fixed capacitive element C0. Signal. Since the capacitance value of the fixed capacitance element C0 is fixed, the phase of the rectangular wave signal appearing on the electrode above the fixed capacitance element C0 is constant, and can be used as a reference signal for detecting the phase difference. . On the other hand, since the capacitance value of the variable capacitance element C5 varies according to the displacement of the weight body 210 in the Z-axis direction, a rectangular wave signal appearing on the electrode (external electrode EE5) above the auxiliary capacitance element CC5. The phase of fluctuates. Eventually, the output signal of the EX-OR circuit 470 becomes a signal indicating this phase fluctuation, and the duty ratio of the rectangular wave obtained at the output terminal TTz indicates the Z-axis direction component of the applied acceleration.

  Here, the frequencies of the rectangular wave signals φ 1 and φ 2 are preferably set to frequencies that do not match the physical resonance frequency of the weight body 210. After all, the principle of the detection circuit shown in FIG. 12 and FIG. 13 is to fix the potential of one electrode in order to detect the capacitance between the common displacement electrode E0 and each of the external electrodes EE1 to EE5 (this In the case of the example, the potential of the common displacement electrode E0 is fixed to the ground potential), and the weight 210 is connected to the other electrode (in this case, each of the external electrodes EE1 to EE5) via a resistance element. A detection AC signal having a frequency that does not match the physical resonance frequency is supplied, and at this time, the phase of the AC signal generated at the other electrode is detected. This utilizes the phenomenon that the time constant of the CR circuit changes and the phase of the obtained AC signal changes when the electrode spacing of each of the variable capacitance elements C1 to C5 changes.

  The acceleration detection circuit using this phase change is a technique disclosed in, for example, Japanese Patent Laid-Open No. 5-346357, and a detailed description thereof is omitted here.

<<< §4. More practical embodiment >>
Subsequently, some of the more practical embodiments of the present invention will be described. The basic principles of the acceleration sensors according to these embodiments are the same as those of the acceleration sensor shown in FIG. 6, but more practical devices are provided.

  (1) First, the acceleration sensor shown in the side sectional view in FIG. 14 is obtained by removing the common displacement electrode E0 from the acceleration sensor shown in FIG. 6, and this is the only difference between the two. As described above, the intermediate substrate 250 is made of a conductive material. Therefore, even if the common displacement electrode E0 is not formed on the upper surface of the intermediate substrate 250, a part of the surface of the conductive intermediate substrate 250 functions as the common displacement electrode E0. In other words, in the acceleration sensor shown in FIG. 14, the common displacement electrode E <b> 0 is configured by a part of the surface of the conductive weight body 210.

  Thus, if the entire intermediate substrate 250 is made of a conductive material, the weight body 210, the flexible portion 220 (supporting means for the weight body 210), and the pedestal portion 230 (a part of the container) Is composed of a physically continuous conductive material, and the common displacement electrode E0 (in this example, as described above, a part of the surface of the weight body 210) and at least a part of the container (this In the case of the example, a conductive path is formed between the pedestal portion 230). For this reason, it becomes possible to wire the detection circuit for the common displacement electrode E0 to the outer surface of the container (the side surface of the pedestal 230). This is a great advantage in simplifying the wiring.

  Each of the acceleration sensors shown in FIGS. 6 and 14 has a three-layer structure in which an upper substrate 150, an intermediate substrate 250, and a lower substrate 300 are stacked. Such a three-layer structure is used. The configuration is an excellent configuration suitable for mass production. For example, if the upper substrate 150 and the lower substrate 300 are constituted by glass substrates and the intermediate substrate 250 is constituted by a silicon substrate, this three-layer structure can be mass-produced in the same process as the semiconductor manufacturing process.

  The intermediate substrate 250 is bonded to the weight body 210, the flexible portion 220 (support means for the weight body 210) that is bonded around the weight body 210 and has flexibility, and the flexible substrate 220. A vacant part S1 is formed on the upper surface of the weight body 210, and a vacant part S2 is formed between the side surface of the weight body 210 and the inner surface of the pedestal part 230. A gap S3 is formed on the lower surface of the weight body 210. As described above, the intermediate substrate 250 becomes a structure having a slightly complicated shape. Such a structure can be obtained by etching a silicon substrate from above and below using a predetermined mask. It can be manufactured relatively easily.

  Further, the upper substrate 150 may be processed to form the groove portion H1 on the upper surface to form the thick portion 151 and the thin portion 152. It is necessary to form fixed electrodes E1 to E5 and external electrodes EE1 to EE5 on the lower surface and the upper surface of the upper substrate 150. This is performed after a metal film is formed on the upper surface and the lower surface of the upper substrate 150. Patterning using a mask may be performed. On the other hand, no special processing is required for the lower substrate 300. Finally, if the upper substrate 150, the intermediate substrate 250, and the lower substrate 300 are anodically bonded in a vacuum chamber, an acceleration sensor having a container whose inside is maintained in a vacuum state is completed.

  (2) In the above description, the dimensions of the structure of the acceleration sensor have not been mentioned at all, but in order to realize an acceleration sensor with sufficient detection sensitivity, the dimensional design of each part is practical. It will be an important issue. In particular, the electrode spacing of the counter electrodes constituting each capacitive element affects the capacitance value of the capacitive element and is a parameter that directly affects the detection sensitivity. Each drawing of the present application is drawn ignoring the dimensional ratio of each part for convenience of illustration, but actually, for example, the dimension d1 (electrode interval of the variable capacitance elements C1 to C5) and the dimension d2 (shown in FIG. 14) are shown. It is necessary to set the electrode interval of the auxiliary capacitance elements CC1 to CC5 to a considerably small value.

According to an experiment conducted by the present inventor, when the variable capacitance elements C1 to C5 are formed by facing a pair of electrodes having an area of about 1 mm ² , the electrode interval is 3 to 10 μm in a state where no acceleration is applied. If it was set so as to be about, a sensor with sufficient detection sensitivity in practical use could be realized. That is, in the case of the example shown in FIG. 14, d1 may be set to about 3 to 10 μm.

  Then, how much should the dimension d2 (thickness of the thin portion 152) shown in FIG. 14 be set? Here, first, let us consider how much the capacitance values of the auxiliary capacitance elements CC1 to CC5 should be set with respect to the capacitance values of the variable capacitance elements C1 to C5. For example, let us consider a case where, in the equivalent circuit shown in FIG. 8B, the change in the capacitance value of the variable capacitance element C1 is taken out as an electrical signal between the connection terminals T0 / T1.

  In this case, it can be seen that the larger the capacitance value of the auxiliary capacitive element CC1, the larger the change in the capacitance value of the variable capacitive element C1 can be extracted as a signal component. This is because the capacitance value between the connection terminals T0 / T1 is set when CC1 = infinity is set in the expression “1 / (1 / C1 + 1 / CC1)” indicating the capacitance value between the connection terminals T0 / T1. = C1, and it can be easily understood considering that only the change in the capacitance value of the variable capacitance element C1 can be taken out. Then, the detection sensitivity increases as the capacitance value of the auxiliary capacitance element CC1 is set larger than the capacitance value of the variable capacitance device C1.

  Now, consider the case where the dimension d1 and the dimension d2 are set to be equal in the structure shown in FIG. In such a setting, if the upper substrate 150 is made of a glass substrate and the relative dielectric constant of the glass is 5, the capacitance value of the auxiliary capacitance element CC1 is five times the capacitance value of the variable capacitance device C1. It turns out that. That is, if the dimension d2 is set equal to the dimension d1, the capacitance value of the auxiliary capacitance element CC1 is five times the capacitance value of the variable capacitance element C1. In order to further increase the detection sensitivity by further increasing the magnification, it is necessary to set the dimension d2 smaller. The auxiliary capacitor elements CC1 to CC1 have a configuration in which the groove H1 for forming the thin part 152 having a small thickness is formed in the upper substrate 150 and the external electrodes EE1 to EE5 are formed on the bottom surface of the groove H1. This is a consideration for setting the electrode interval d2 of CC5 as small as possible.

  Eventually, in order to ensure sufficient detection sensitivity in practical use, it is necessary to set d1 = about 3 to 10 μm and d2 to the same size or less. However, when the dimension d2 is set to about 3 to 10 μm, it is difficult to ensure sufficient rigidity for the thin portion 152, and another problem of bending of the thin portion 152 occurs. If d2 is set to be small, for example, when using a structure whose interior is kept in a vacuum as in the example shown in FIG. 15, the thin portion 152 may bend inward due to the atmospheric pressure P applied from the outside. become. Moreover, since the amount of deflection varies depending on the atmospheric pressure at that time, it causes a measurement error depending on the use environment (such as weather).

  The embodiment shown in FIG. 16 illustrates a first approach to address this problem. The acceleration sensor shown in FIG. 16 includes a reinforcing material inside the groove H1 formed on the upper surface of the upper substrate 150 in the acceleration sensor shown in FIG. 14 (that is, in the groove where the external electrodes EE1 to EE5 are formed). In this way, the reinforcing material filling portion 160 is formed. As the reinforcing material, any material such as silicon oxide, silicon nitride, or a polymer film can be used. However, in order to eliminate a measurement error due to the influence of thermal expansion, the material of the upper substrate 150 is heated as much as possible. It is preferable to use a material having a close expansion coefficient. Note that the wiring between the external electrodes EE1 to EE5 and the connection terminals T1 to T5 may be performed before the reinforcing material is filled.

  (3) A second approach for dealing with the above problem is a method of providing a signal extraction unit for extracting a signal at a location different from the functional unit that performs the original function of the sensor. The embodiment shown in FIG. 17 shows a solution based on this second approach. The acceleration sensor shown in FIG. 17 includes a right-side function unit A and a left-side signal extraction unit B.

  This sensor also has a structure in which three layers of an upper substrate 180 made of a glass substrate, an intermediate substrate 280 made of a silicon substrate, and a lower substrate 380 made of a glass substrate are laminated. FIG. 18 is a top view of the intermediate substrate 280, and FIG. 19 is a cross-sectional view showing a state in which the intermediate substrate 280 is cut along a cutting line 19-19.

  As shown in FIG. 19, the peripheral portion of the intermediate substrate 280 is configured by a pedestal portion 235, and the right side of the partition portion 236 is the functional portion A and the left side is the signal extraction portion B. A weight body 210 is disposed inside the functional part A, and a gap S <b> 2 is formed between the weight body 210 and the inner surface of the pedestal part 235. On the other hand, a gap portion S4 is formed inside the signal extraction portion B. The point that the weight body 210 is supported by the flexible portion 220 is exactly the same as the previous embodiments.

  20 and 21 are a top view and a bottom view of the upper substrate 180, respectively. In these drawings, the positions of the weight body 210 and the pedestal portion 235 are indicated by broken lines. As shown in FIG. 20, grooves H2 and H3 are dug on the upper surface of the upper substrate 180, external electrodes FF1 to FF5 are formed at the bottom of the groove H2, and at the bottom of the groove H3. A common external electrode FF0 is formed. Further, the connection terminals T1 to T5 are arranged beside the groove H2, and wiring is made from the connection terminals T1 to T5 to the external electrodes FF1 to FF5 so as to straddle the stepped portion of the groove H2. . Similarly, a connection terminal T0 is disposed beside the groove H3, and wiring is made from the connection terminal T0 to the common external electrode FF0 so as to straddle the step portion of the groove H3.

  FIG. 17 corresponds to a side sectional view of the sensor cut along the XZ plane, and shows the sectional shapes of the grooves H2 and H3. That is, the upper substrate 180 includes a thick part 181, a thin part 182 located below the groove part H <b> 2, and a thin part 183 located below the groove part H <b> 3. In FIG. 17, only the external electrode FF2 arranged on the X axis appears on the bottom surface of the groove H2. Further, the connection terminals T0 to T5 shown in FIG. 20 and the wiring extending therefrom are not shown in FIG.

  FIG. 21 shows a planar shape of each electrode and wiring portion formed on the lower surface of the upper substrate 180. The fixed electrodes E1 to E5 shown in FIG. 21 perform the same functions as the fixed electrodes E1 to E5 shown in FIG. That is, the fixed electrodes E1 to E5 shown in FIG. 21 are electrodes facing a common displacement electrode E0 (not shown) formed by a part of the surface of the weight body 210, and The variable capacitance elements C1 to C5 are formed.

  On the other hand, as shown on the left side of FIG. 21, auxiliary electrodes F <b> 1 to F <b> 5 are formed on the lower surface of the upper substrate 180. Here, the auxiliary electrodes F1 to F5 shown in FIG. 21 are opposed to the external electrodes FF1 to FF5 shown in FIG. 20, respectively, and auxiliary capacitance elements CC1 to CC5 are formed by the opposing electrodes. For example, FIG. 17 shows a state in which the auxiliary electrode F2 and the external electrode FF2 are opposed to each other with the thin portion 182 interposed therebetween, and the auxiliary capacitor element CC2 is formed by the pair of counter electrodes. Become.

  Further, as shown in FIG. 21, the auxiliary electrodes F1 to F5 and the fixed electrodes E1 to E5 are electrically connected by wiring portions L1 to L5, respectively. As shown in FIG. 17, the upper end of the partition part 236 does not reach the lower surface of the upper substrate 180 in order to ensure a gap for passing these wiring parts L1 to L5.

  After all, in this acceleration sensor, the variable capacitance elements C1 to C5 and the auxiliary capacitance elements CC1 to CC5 are respectively connected in series, and for example, detection using the detection circuit shown in FIG. 9 becomes possible. . However, in the case of the acceleration sensor shown in FIG. 14, since the variable capacitance elements C1 to C5 and the auxiliary capacitance elements CC1 to CC5 are formed in the same region, the electrode interval (dimension d2) of the auxiliary capacitance elements CC1 to CC5 is reduced. When set, as shown in FIG. 15, the thin portion 152 is bent by the atmospheric pressure P, and there is a problem that the electrode spacing (dimension d1) of the variable capacitance elements C1 to C5 is also affected. Such a problem does not occur in the acceleration sensor shown in FIG.

  In the case of the acceleration sensor shown in FIG. 17, the variable capacitance elements C1 to C5 necessary for the original detection function of the sensor are provided at the positions of the common displacement electrode E0 provided on the weight body 210 and the inner surface of the container opposite to the common displacement electrode E0. The fixed electrodes E1 to E5 are arranged in the functional part A. On the other hand, the auxiliary capacitance elements CC1 to CC5 necessary for taking out signals to the outside are auxiliary electrodes F1 to F5 provided at positions different from the fixed electrodes E1 to E5 on the inner surface of the container, and the container facing the auxiliary electrodes F1 to F5. It is composed of external electrodes FF1 to FF5 provided at positions on the outer surface, and is arranged in the signal extraction part B. Moreover, the fixed electrodes E1 to E5 and the auxiliary electrodes F1 to F5 are electrically connected by the wiring portions L1 to L5, respectively. The acceleration sensor having such a configuration can detect acceleration based on the capacitance between the common displacement electrode E0 and each of the external electrodes FF1 to FF5, as in the embodiments described above.

  In the acceleration sensor having such a configuration, even if the electrode spacing (thickness of the thin portion 182) of the auxiliary capacitance elements CC1 to CC5 is set small and the thin portion 182 is bent by the atmospheric pressure P, the measured value is obtained. Will not have a significant impact. This is because even if the thin portion 182 is bent, the electrode spacing of the auxiliary capacitive elements CC1 to CC5 (thickness of the thin portion 182) does not vary greatly, and the electrode spacing of the variable capacitive elements C1 to C5 also varies greatly. This is because no problem occurs.

  In the case of the acceleration sensor shown in FIG. 17, wiring to the common displacement electrode E0 (the upper surface of the weight body 210) can also be performed from the upper surface of the upper substrate 180. As illustrated, a common external electrode FF0 is formed on the bottom surface of the groove H3, and the common external electrode FF0 is opposed to the top surface of the pedestal portion 235 with an insulating layer (thin portion 183) interposed therebetween. Therefore, the auxiliary capacitive element CC0 is formed by the upper surface of the base portion 235 and the common external electrode FF0. Moreover, since the entire intermediate substrate 280 is made of a conductive material, the upper surface of the pedestal portion 235 becomes the equipotential surface of the common displacement electrode E0. Eventually, the common external electrode FF0 is connected to the common displacement electrode E0 in an alternating current manner via the auxiliary capacitance element CC0. Therefore, the common external electrode FF0 is connected between the common external electrode FF0 and the external electrodes FF1 to FF5. If a detection circuit for detecting acceleration based on the electrostatic capacity of is provided, a necessary detection operation can be performed.

  Specifically, in the circuit shown in FIG. 9, since the connection terminal T0 is connected to the common external electrode FF0, between the connection terminal T0 and the common displacement electrode E0 in the circuit diagram of FIG. A circuit to which the auxiliary capacitance element CC0 is added is a detection circuit used in the acceleration sensor shown in FIG. The acceleration sensor shown in FIG. 17 has an advantage that all wiring can be performed on the upper surface of the upper substrate 180.

<<< §5. Upper substrate manufacturing process >>
Here, an example of a process suitable for manufacturing an upper substrate will be described in the case where the sensor according to the present invention is constituted by a laminate of three substrates, an upper substrate, an intermediate substrate, and a lower substrate.

  As described above, in the upper substrate 150 in the embodiment shown in FIG. 14, it is practically preferable to set the thickness d2 of the thin portion 152 to about 3 to 10 μm. Similarly, in the upper substrate 180 in the embodiment shown in FIG. 17, it is preferable to set the thickness of the thin portion 182 and the thin portion 183 to about 3 to 10 μm. Here, a process suitable for manufacturing an upper substrate having such a thin portion having a very small thickness will be described.

  The feature of this process is that the upper substrate is constituted by a two-layer structure of a silicon substrate and a glass substrate. FIG. 22 is a side sectional view showing a modification in which an upper substrate 190 having a two-layer structure is used instead of the upper substrate 180 of the acceleration sensor shown in FIG. The other components of the modification shown in FIG. 22 are exactly the same as those of the acceleration sensor shown in FIG. 17, and of course, the operation principle is exactly the same.

  As shown in the figure, the upper substrate 190 shown in FIG. 22 includes a lower layer portion 191 made of a glass substrate and an upper layer portion 192 made of a silicon substrate. Here, for the sake of convenience, a diagram ignoring the ratio of the thickness of the lower layer portion 191 and the upper layer portion 192 is shown, but the thickness of the lower layer portion 191 is actually about 3 to 10 μm, whereas the upper layer The thickness of the part 192 is about 300 μm.

  In the upper substrate 190, the groove portions H4 and H5 are formed by through holes penetrating the front and back of the upper layer portion 192. The common external electrode FF0 and the external electrodes FF1 to FF5 are formed on the upper surface of the lower layer portion 191. If the upper substrate 190 has such a two-layer structure, the electrode spacing of the auxiliary capacitance elements CC1 to CC5 can be determined by the thickness of the lower layer portion 191. Therefore, the capacitance values of the auxiliary capacitance elements CC1 to CC5 can be determined. If it is desired to set a larger value, the lower layer portion 191 having a smaller thickness may be created. However, it is difficult to prepare the lower layer portion 191 having a thickness of about 3 to 10 μm as a single glass substrate. Therefore, the present inventor has conceived a method of manufacturing the upper substrate 190 by the following process.

  23 and 24 are side sectional views showing a method of manufacturing the upper substrate 190. First, as shown in FIG. 23 (a), a silicon substrate 10 having a thickness of about 300 μm is prepared, and a through hole H (which will later become a groove portion) is formed in a predetermined portion (region where an external electrode needs to be formed). ). Here, the silicon substrate 10 is etched using an anisotropic etching solution such as KOH to form tapered through holes H that expand upward. Thus, if the side surface of the through hole H is tapered, it is convenient to form a wiring for the external electrode later.

  Subsequently, a glass substrate 20 having a thickness of about 300 μm is prepared, and the glass substrate 20 is bonded to the lower surface of the silicon substrate 10 as shown in FIG. Both are preferably joined by anodic bonding. The anodic bonding is a bonding method that is very suitable for bonding a silicon substrate and a glass substrate, and enables a very firm bonding. Thus, when a structure composed of two layers of the silicon substrate 10 and the glass substrate 20 is formed, the through hole H functions as the groove portion H.

  Next, the lower surface of the glass substrate 20 in the two-layer structure is polished to form a glass substrate 25 having a thickness of about 3 to 10 μm, as shown in FIG. Thus, by polishing the glass substrate 20 in a state of being bonded to the silicon substrate 10, the glass substrate 25 having a thickness of about 3 to 10 μm can be formed without any problem. With the above, the basic structure of the upper substrate 190 is completed.

  Subsequently, a process of forming an external electrode at the bottom of the groove H is performed. In the subsequent processes, the upper substrate 190 is bonded to the upper surface of the pedestal 230 (the intermediate substrate 280 may be formed of a silicon substrate). (This bonding can also be performed by anodic bonding), or can be performed before bonding.

  First, as shown in FIG. 24A, a silicon oxide film 15 is formed on the upper surface of the silicon substrate 10. This oxide film 15 functions as an insulating film for a wiring layer to be formed later. This film is not necessarily a silicon oxide film as long as it can function as an insulating film, but the silicon oxide film 15 is easily formed by subjecting the surface of the silicon substrate 10 to oxidation. Therefore, in practice, it is preferable to use the oxide film 15 as the insulating film. Of course, instead of using the method of surface oxidation of the silicon substrate 10, a method of depositing an oxide film or another insulating film on the surface of the silicon substrate 10 may be used.

  Next, as shown in FIG. 24B, a metal film 30 made of aluminum or the like is formed on the upper surface of the oxide film 15 and the groove H. Instead of the metal film 30, a layer made of an arbitrary conductive material may be formed. Then, as shown in FIG. 24 (c), the metal film 30 is patterned, and the external electrode 35 located at the bottom of the groove H and the wiring 36 for the external electrode 35 (extends from the side surface of the groove H to the outside of the groove). Part).

  Finally, as shown in FIG. 24 (d), a reinforcing material layer 40 is formed on the entire top surface of the substrate. The reinforcing material layer 40 may be made of a material such as silicon oxide, silicon nitride, or a polymer film. The reinforcing material layer 40 functions to reinforce the inside of the groove H, and it is sufficient that at least the inside of the groove H can be filled. Since the thickness of the glass substrate 25 is about 3 to 10 μm as described above, it is possible to prevent a part of the glass substrate 25 from being bent by atmospheric pressure by filling the groove H with a reinforcing material. Of course, as in the example shown in FIG. 17 and FIG. 22, the reinforcing material layer 40 is not necessarily required when the functional portion A and the signal extraction portion B are separately provided. The filling process may be omitted.

  The manufacturing process of the upper substrate 190 in the acceleration sensor shown in FIG. 22 has been described above. However, the manufacturing process of the upper substrate based on the above procedure can also be applied to the case of manufacturing the upper substrate 150 shown in FIG.

<<< §6. Embodiment in which fixed electrode is omitted >>>
Next, another embodiment will be described with reference to FIG. The acceleration sensor shown in FIG. 25 is a further simplification of the structure of the acceleration sensor shown in FIG. 14. In the acceleration sensor shown in FIG. 14, fixed electrodes E1 to E5 formed on the lower surface of the upper substrate 150 are provided. It has been deleted. Therefore, the electrodes in this sensor are only the common displacement electrode E0 constituted by the upper surface of the weight body 210 and the external electrodes EE1 to EE5 (see FIG. 7 for a plan view) formed on the upper surface of the upper substrate 150. .

  These electrodes form variable capacitance elements C1 to C5. For example, the variable capacitor C1 is formed by the external electrode EE1 and a part of the common displacement electrode E0 facing the external electrode EE1. The electrode interval of the variable capacitance element C1 is the illustrated dimension (d1 + d2). The dielectric constant of the portion corresponding to the dimension d1 is a vacuum dielectric constant when the inside of the container is maintained in a vacuum, and the dielectric constant of the portion corresponding to the dimension d2 is the material (for example, the thin portion 152) , Glass).

  As described above, the variable capacitance elements C1 to C5 in the acceleration sensor shown in FIG. 25 are capacitance elements constituted by the counter electrodes sandwiching two types of media having different dielectric constants. The principle of detecting the acceleration based on the above is exactly the same as the detection principle of each acceleration sensor described so far. That is, if any detection circuit capable of measuring the capacitance value between the common displacement electrode E0 and each of the external electrodes EE1 to EE5 is used, it is possible to detect each coordinate axis direction component of the applied acceleration.

  In short, in the embodiment shown in FIG. 25, between the common displacement electrode E0 provided on the weight body 210 and the external electrodes EE1 to EE5 provided at positions facing the common displacement electrode E0 on the outer surface of the container. The acceleration is detected based on the capacitance. If the entire intermediate substrate 250 is made of a conductive material, wiring to the common displacement electrode E0 may be performed on the outer surface of the pedestal portion 230, so that there is no need to perform wiring inside the container.

  However, in order to ensure practical detection sensitivity using the acceleration sensor shown in FIG. 25, it is necessary to set the electrode interval (d1 + d2) of the variable capacitance elements C1 to C5 to be considerably small, and the thickness of the thin portion 152. It is preferable to set d2 as small as possible. Therefore, practically, the groove H1 formed on the upper surface of the upper substrate 150 is filled with some reinforcing material (which may be silicon oxide, silicon nitride, polymer film, or the like), as in the modification shown in FIG. It is preferable to reinforce by the reinforcing material filling portion 160. In this case, wiring between the external electrodes EE1 to EE5 and the connection terminals T1 to T5 is performed before the reinforcing material filling operation.

<<< §7. Various modifications >>
Although the present invention has been described above with reference to some embodiments illustrated in the drawings, the present invention is not limited to these embodiments and can be implemented in various other forms.

  For example, in the embodiments described so far, a plurality of five displacement electrodes E6 to E10 (or a physically single common displacement electrode E0 that performs the same function as these) and each of these displacement electrodes 5 are opposed to each other. A pair of fixed electrodes E1 to E5 and five external electrodes EE1 to EE5 that face each of these fixed electrodes are formed (or five auxiliary electrodes F1 to F5 that face each of these auxiliary electrodes). 5 external electrodes FF1 to FF5 are formed) and detection is performed using 5 sets of variable capacitance elements C1 to C5 and 5 sets of auxiliary capacitance elements CC1 to CC5. The number of elements does not necessarily need to be set to 5, but only a necessary number may be prepared according to the coordinate axis components necessary for detection.

  Further, the structure of the flexible portion 220 for supporting the weight body 210 is not limited to the structure shown in the above-described embodiments. The flexible portion 220 may have any structure as long as it has a function of supporting the weight body 210 in a manner that can be displaced in the housing body.

  FIG. 27 is a top view of an intermediate substrate 290 which is a modification of the intermediate substrate 280 shown in FIG. The only difference is that the weight body 210 and the flexible part 220 in FIG. 18 are replaced with the weight body 215 and the flexible part 225 in FIG. 27, and the structure of the other parts is exactly the same. It is. In the modification shown in FIG. 27, as shown, the weight body 215 has a structure having four wing-like portions when viewed from above. The flexible portion 225 includes a plate-like frame body that surrounds the weight body 215 and four beam portions BM separated by the slit SL. The slit SL forms a through groove that separates the weight body 215 and the flexible portion 225. FIG. 28 is a transverse sectional view of the weight body 215, and the position of the slit SL is indicated by a broken line.

  As described above, when the weight body 215 is physically separated by the slit SL, the weight body 215 is supported only by the four beam portions BM. Compared with this structure, a structure in which the weight body 215 is more easily displaced can be realized. Of course, such a structure in which the weight body is isolated by the slit and the weight body is supported by the beam portion is also applicable to the embodiment shown in FIG.

  In addition, as shown in FIG. 17 and FIG. 22, if a structure in which the functional part A and the signal extraction part B are provided separately, the phenomenon of “the bending of the thin part due to the atmospheric pressure” can be dealt with. As already described in §4, on the contrary, if this phenomenon is used, it becomes possible to test the sensor. For example, consider a case in which a sensor having the structure shown in FIG. 17 and having a vacuum inside the container is commercialized. In such a sensor, it is normal for the inside of the container to be in a vacuum, and if for some reason, the wall surface of the container is cracked and the inside is at atmospheric pressure, the proper operation is correct. Can not do.

  Therefore, if a mechanism for detecting the bending state of the thin part 182 is provided, it is possible to test whether or not the inside of the container is maintained in a vacuum state. This can be detected when the atmospheric pressure is reached. That is, assuming that the state shown in FIG. 17 is a normal state (the gap S4 is in a vacuum state), if an air leak occurs, the thin portion 182 is moved to the outside by the pressure of the air that has entered the inside. It bends and swells. If this can be detected by some kind of detection mechanism, it can be tested whether the inside of the sensor is in a normal state maintained in a vacuum.

  In order to detect the bending state of the thin portion 182, for example, the capacitance value of a capacitive element constituted by a pair of test electrodes provided so as to sandwich the thin portion 182 may be monitored, A piezoresistive element or the like may be formed in the thin portion 182 and the change in electrical resistance of this element may be monitored. Of course, the mechanism for detecting the bending state of the thin portion 182 can be used not only for testing whether or not the inside of the sensor is maintained in a vacuum state, but can also function as a general barometer.

  Next, application to an angular velocity sensor will be described. In the above embodiments, an example in which the present invention is applied to an acceleration sensor has been described. However, a general structure that should be referred to as a sensor main body can be used for an acceleration sensor or an angular velocity sensor. The present invention is applicable not only to acceleration sensors but also to angular velocity sensors.

  In the angular velocity sensor, the angular velocity is detected by detecting the Coriolis force acting on the weight body in a state where the weight body is vibrated in a predetermined direction. Therefore, it is necessary to prepare excitation means for vibrating the weight body, but any of the variable capacitance elements C1 to C5 in the structure described so far as the acceleration sensor can function as the excitation means. is there.

  Therefore, an excitation means for supplying an excitation AC signal having a frequency matching the physical resonance frequency of the weight body between a specific external electrode and a corresponding displacement electrode is prepared, and the excitation AC If a signal is supplied, the weight body can be vibrated at the resonance frequency. In this way, when the weight body vibrates due to the supply of the excitation AC signal, the angular velocity can be detected by detecting the displacement generated in the weight body due to the Coriolis force acting as an external force.

  For example, if the detection circuit shown in FIG. 9 is applied to the sensor body having the structure shown in FIG. 6, the X-axis direction component, the Y-axis direction component, and the Z-axis direction component of the applied acceleration can be detected. As described above, an acceleration sensor capable of achieving the above can be realized. However, if the detection circuit shown in FIG. 29 is applied to the sensor body shown in FIG. 6, an angular velocity sensor capable of detecting the angular velocity ωx around the X axis and the angular velocity ωy around the Y axis can be realized.

  In the circuit shown in FIG. 29, the portions related to the capacitive elements C1 and CC1 and the capacitive elements C2 and CC2 are caused by the phase difference between the potential of the connection terminal T1 and the potential of the connection terminal T2, as in the circuit shown in FIG. This is the part that functions to detect the displacement of the weight body in the X-axis direction. That is, a rectangular wave signal φ1 from the AC power supply 400 is applied to the connection terminal T1 via the resistance element R1, and a rectangular wave signal φ2 from the AC power supply 405 is applied to the connection terminal T2 via the resistance element R2. It is done.

  In this embodiment, the capacitance values of the capacitive elements CC1 and CC2 are equal, the resistance values of the resistance elements R1 and R2 are equal, and the capacitance values of the capacitive elements C1 and C2 when the weight body is not displaced. Are set to be equal, and the AC power supplies 400 and 405 are supplied with rectangular wave signals having the same frequency and different phases, so that the capacitance value of the capacitive element C1 and the capacitance value of the capacitive element C2 Are equal, the phase difference between the voltage signal appearing at the connection terminal T1 and the voltage signal appearing at the connection terminal T2 is equal to the phase difference between the AC power supplies 400 and 405. However, when the weight body is displaced in the X-axis direction, a difference occurs in the capacitance values of the capacitive elements C1 and C2, so that the time constant of the CR circuit changes, and the voltage signal appearing at the connection terminal T1 and the connection terminal T2 change. A change occurs in the phase difference from the voltage signal that appears. The EX-OR circuit 460 is a circuit that detects this phase difference, and the EX-OR circuit 460 outputs a rectangular wave signal having a duty ratio corresponding to this phase difference.

  Similarly, the portions related to the capacitive elements C3 and CC3 and the capacitive elements C4 and CC4 have a function of detecting the displacement of the weight body in the Y-axis direction based on the phase difference between the potential of the connection terminal T3 and the potential of the connection terminal T4. It is the part that plays. That is, a rectangular wave signal φ1 from the AC power supply 400 is applied to the connection terminal T3 via the resistance element R3, and a rectangular wave signal φ2 from the AC power supply 405 is applied to the connection terminal T4 via the resistance element R4. It is done.

  Here, the capacitance values of the capacitance elements CC3 and CC4 are equal, the resistance values of the resistance elements R3 and R4 are equal, and the capacitance values of the capacitance elements C3 and C4 when the weight body is not displaced are also equal. Since the rectangular wave signals having the same frequency and different phases are supplied from the AC power supplies 400 and 405, the capacitance value of the capacitive element C3 and the capacitance value of the capacitive element C4 are set. If they are equal, the phase difference between the voltage signal appearing at the connection terminal T3 and the voltage signal appearing at the connection terminal T4 is equal to the phase difference between the AC power supplies 400 and 405. However, when the weight body is displaced in the Y-axis direction, a difference occurs in the capacitance values of the capacitive elements C3 and C4, so that the time constant of the CR circuit changes and the voltage signal appearing at the connection terminal T3 and the connection terminal T4 are changed. A change occurs in the phase difference from the voltage signal that appears. The EX-OR circuit 470 is a circuit that detects this phase difference, and the EX-OR circuit 470 outputs a rectangular wave signal having a duty ratio corresponding to this phase difference.

  On the other hand, the portions related to the capacitive elements C5 and CC5 are portions that perform the function of exciting the weight body in the Z-axis direction. That is, the AC power source 500 is connected between the connection terminals T0 (ground) and T5. This AC power supply 500 functions as an excitation means for supplying an excitation AC signal (in this example, a sine wave signal). In this way, when the excitation AC signal from the AC power supply 500 is supplied between the connection terminals T0 / T5, the weight body is driven in the Z-axis direction at the frequency of the excitation AC signal by the Coulomb force generated between the electrodes E0 / E5. Vibrate. The angular velocity is thus detected by detecting the Coriolis force acting on the weight body in a state where the weight body is vibrated in the Z-axis direction.

  That is, when the weight body is vibrated in the Z-axis direction, when the angular velocity ωy around the Y-axis acts on the weight body, Coriolis force is applied to the weight body in the X-axis direction. Is displaced in the X-axis direction. As a result, as described above, a signal corresponding to the displacement of the weight body in the X-axis direction is output from the EX-OR circuit 460. The synchronous detection circuit 480 executes detection processing synchronized with the excitation AC signal from the AC power supply 500, and shows a signal indicating displacement in the X-axis direction output from the EX-OR circuit 460 as an angular velocity ωy around the Y-axis. The signal is converted into a signal and output to the output terminal Tωy.

  On the other hand, when an angular velocity ωx around the X axis acts on the weight body in a state where the weight body is vibrated in the Z-axis direction, Coriolis force is applied to the weight body in the Y-axis direction. Is displaced in the Y-axis direction. As a result, as described above, a signal corresponding to the displacement of the weight body in the Y-axis direction is output from the EX-OR circuit 470. The synchronous detection circuit 490 executes a detection process synchronized with the excitation AC signal from the AC power supply 500, and a signal indicating the displacement in the Y-axis direction output from the EX-OR circuit 470 indicates the angular velocity ωx around the X axis. The signal is converted into a signal and output to the output terminal Tωx.

  As described above, the excitation AC signal supplied from the AC power supply 500 is an AC signal having a frequency (generally about 4 to 20 kHz) that matches the physical resonance frequency of the weight body. The AC signal for detection supplied from the AC power sources 400 and 405 has an AC signal having a frequency that does not match the physical resonance frequency of the weight body (generally, it may be set to about 200 to 500 kHz). Is preferable.

It is a sectional side view which shows an example of the conventional acceleration sensor. FIG. 2 is a bottom view of an upper substrate 100 in the conventional acceleration sensor shown in FIG. 1. FIG. 2 is a top view of an intermediate substrate 200 in the conventional acceleration sensor shown in FIG. It is a sectional side view of the conventional acceleration sensor which used the common electrode for the intermediate substrate side (the connection part to each terminal is shown with a wiring diagram). FIG. 5 is a top view of an intermediate substrate 200 in the conventional acceleration sensor shown in FIG. 4. It is a sectional side view of the acceleration sensor which concerns on fundamental embodiment of this invention. It is a top view of the upper board | substrate 150 in the acceleration sensor shown in FIG. Fig. (A) is a partial sectional side view for explaining the operation of the acceleration sensor shown in Fig. 6 (connections to each terminal are shown by wiring diagrams), and Fig. (B) is an equivalent circuit diagram thereof. . It is a circuit diagram which shows an example of the detection circuit used for the acceleration sensor shown in FIG. FIG. 10 is a signal waveform diagram for explaining the operation of the detection circuit shown in FIG. 9. FIG. 10 is another signal waveform diagram for explaining the operation of the detection circuit shown in FIG. 9. It is a circuit diagram which shows another detection circuit used for the acceleration sensor shown in FIG. It is a circuit diagram which shows another detection circuit used for the acceleration sensor shown in FIG. FIG. 7 is a side sectional view showing a modification in which the upper surface of the weight body 210 is a common displacement electrode E0 in the acceleration sensor shown in FIG. FIG. 15 is a side sectional view showing that the detection operation by the acceleration sensor shown in FIG. 14 is affected by atmospheric pressure. It is a sectional side view which shows the example which gave the 1st device for removing the influence of atmospheric pressure with respect to the acceleration sensor shown in FIG. It is a sectional side view which shows the example which gave the 2nd device for eliminating the influence of atmospheric pressure with respect to the acceleration sensor shown in FIG. FIG. 18 is a top view of an intermediate substrate 280 in the acceleration sensor shown in FIG. 17. FIG. 19 is a cross-sectional view showing a state where the acceleration sensor shown in FIG. 17 is cut along a cutting line 19-19. FIG. 18 is a top view of an upper substrate 180 in the acceleration sensor shown in FIG. 17. FIG. 18 is a bottom view of an upper substrate 180 in the acceleration sensor shown in FIG. 17. It is a sectional side view which shows the modification of the acceleration sensor shown in FIG. FIG. 23 is a side sectional view showing a first half of a manufacturing process of the upper substrate 190 in the acceleration sensor shown in FIG. 22. FIG. 23 is a side sectional view showing a latter half of the manufacturing process of the upper substrate 190 in the acceleration sensor shown in FIG. 22. It is a sectional side view which shows the acceleration sensor which concerns on another embodiment of this invention. FIG. 26 is a side sectional view showing a modification of the acceleration sensor shown in FIG. 25. FIG. 20 is a top view showing a modification of the intermediate substrate 280 shown in FIG. FIG. 28 is a transverse sectional view of a weight body 215 in the intermediate substrate 290 shown in FIG. 27. It is a circuit diagram which shows an example of the detection circuit used when using the acceleration sensor shown in FIG. 6 as an angular velocity sensor.

Explanation of symbols

10 ... Silicon substrate 15 ... Oxide film 20 ... Glass substrate 25 ... Glass substrate (polished)
DESCRIPTION OF SYMBOLS 30 ... Metal film 35 ... External electrode part 36 of metal film ... Wiring part 40 of metal film ... Reinforcement material layer 100 ... Upper substrate 150 ... Upper substrate 151 ... Thick part 152 ... Thin part 160 ... Reinforcement material filling Part 180 ... Upper substrate 181 ... Thick parts 182 and 183 ... Thin part 190 ... Upper substrate 191 ... Lower layer part 192 ... Upper layer part 200 ... Intermediate substrates 210 and 215 ... Weight bodies 220 and 225 ... Flexible parts 230 and 235 ... Pedestal portion 236 ... Partition portion 250 ... Intermediate substrate 280, 290 ... Intermediate substrate 300 ... Lower substrate 380 ... Lower substrate 400, 405 ... AC power supply 410, 420 ... Differential circuit 430, 440, 450 ... Detection circuit 460, 470 ... EX- OR circuit 480, 490 ... synchronous detection circuit B ... signal extraction part BM ... beam part C0 ... fixed capacitance element C1-C5 ... variable capacitance element CC1-CC5 ... auxiliary capacitance element DESCRIPTION OF SYMBOLS 1, d2 ... Size E0 ... Common displacement electrode E1-E5 ... Fixed electrode E6-E10 ... Displacement electrode EE1-EE5 ... External electrode F1-F5 ... Auxiliary electrode FF0 ... Common external electrode FF1-FF5 ... External electrode G ... Weight body Center of gravity H ... groove / through holes H1-H5 ... groove L1-L5 ... wiring P ... atmospheric pressure R1-R4 ... resistive elements S1-S4 ... gap SL ... slits T0, T1-T5 ... connecting terminals Tx, Ty, Tz, TTx, TTz, Tωx, Tωy ... output terminals V0, V1 to V5, Vx, Vy, Yz ... signal voltages φ1, φ2 ... rectangular wave signal φ3 ... sine wave signal

Claims (21)

A weight body, a housing body for housing the weight body, support means for supporting the weight body in the housing body in a displaceable manner, and the weight body due to an external force to the housing body A sensor having a function of detecting an applied acceleration or an angular velocity based on a detection result of the displacement detection means.
The displacement detecting means is a displacement electrode provided on the weight body, a fixed electrode provided at a position facing the displacement electrode on the inner surface of the container, and a position facing the fixed electrode on the outer surface of the container. An acceleration / angular velocity sensor, comprising: an external electrode provided on the sensor; and a detection circuit that detects acceleration or angular velocity based on a capacitance between the displacement electrode and the external electrode. The sensor according to claim 1, wherein
A plurality of n displacement electrodes, n fixed electrodes facing each of these displacement electrodes, n external electrodes facing each of these fixed electrodes, each displacement electrode and each corresponding external electrode, An acceleration / angular velocity sensor, comprising: a detection circuit that detects acceleration or angular velocity based on a capacitance between the two. A weight body, a housing body for housing the weight body, support means for supporting the weight body in the housing body in a displaceable manner, and the weight body due to an external force to the housing body A sensor having a function of detecting an applied acceleration or an angular velocity based on a detection result of the displacement detection means.
The displacement detection means includes a displacement electrode provided on the weight body, an external electrode provided at a position facing the displacement electrode on the outer surface of the container, and an electrostatic capacitance between the displacement electrode and the external electrode. An acceleration / angular velocity sensor, comprising: a detection circuit that detects acceleration or angular velocity based on capacitance. The sensor according to claim 3, wherein
Acceleration or angular velocity is detected based on the capacitance between a plurality of n displacement electrodes, n external electrodes facing each of these displacement electrodes, and each displacement electrode and each corresponding external electrode. And an acceleration / angular velocity sensor. A weight body, a housing body for housing the weight body, support means for supporting the weight body in the housing body in a displaceable manner, and the weight body due to an external force to the housing body A sensor having a function of detecting an applied acceleration or an angular velocity based on a detection result of the displacement detection means.
The displacement detection means is located at a position different from the displacement electrode provided on the weight body, the fixed electrode provided on the inner surface of the container opposite to the displacement electrode, and the fixed electrode on the inner surface of the container. An auxiliary electrode provided on the outer surface, a wiring portion that electrically connects the fixed electrode and the auxiliary electrode, an external electrode provided at a position facing the auxiliary electrode on the outer surface of the container, the displacement electrode, and the An acceleration / angular velocity sensor, comprising: a detection circuit that detects acceleration or angular velocity based on capacitance between the external electrode and the external electrode. The sensor according to claim 5, wherein
A plurality of n displacement electrodes, n fixed electrodes facing each of these displacement electrodes, n auxiliary electrodes connected to each of these fixed electrodes, and n sheets facing each of these auxiliary electrodes An acceleration / angular velocity sensor, comprising: an external electrode; and a detection circuit that detects acceleration or angular velocity based on capacitance between each displacement electrode and each corresponding external electrode. The sensor according to any one of claims 2, 4 and 6,
An acceleration / angular velocity sensor, wherein n displacement electrodes are physically constituted by a single common displacement electrode. The sensor according to claim 7, wherein
An acceleration / angular velocity sensor, wherein the weight body is made of a conductive material, and a common displacement electrode is formed by a part of the surface of the weight body. The sensor according to claim 7 or 8,
At least a part of the structure composed of the weight body, the support means, and the container is made of a physically continuous conductive material so that a conductive path is formed between the common displacement electrode and at least a part of the container. Acceleration / Angular velocity sensor. The sensor according to claim 9, wherein
A common external electrode is provided at a predetermined position on the outer surface of the container and facing the equipotential surface of the common displacement electrode via the insulating layer,
An acceleration / angular velocity sensor, wherein a detection circuit detects acceleration or angular velocity based on a capacitance between the common external electrode and each external electrode. The sensor according to any one of claims 2, 4 and 6,
Between the specific external electrode and the corresponding displacement electrode, there is an excitation means for supplying an alternating current signal for excitation having a frequency that matches the physical resonance frequency of the weight body,
The displacement detection means detects the displacement caused by the Coriolis force acting as an external force on the weight body in a state where the weight body vibrates due to the supply of the excitation AC signal. An angular velocity sensor that performs detection. The sensor according to any one of claims 1 to 11,
An angular velocity sensor characterized in that the container has a sealed structure and the inside is maintained in a vacuum. The sensor according to any one of claims 1 to 12,
It has a three-layer structure in which an upper substrate, an intermediate substrate, and a lower substrate are stacked,
A weight body, a flexible portion bonded around the weight body, and a pedestal portion bonded around the flexible portion are formed by the intermediate substrate, A gap is formed between the side surface of the weight body and the inner surface of the pedestal portion,
The lower surface of the upper substrate is bonded to the upper surface of the pedestal portion, and a gap is formed between the upper surface of the weight body and the lower surface of the upper substrate,
A displacement electrode is formed on the upper surface of the weight body, and an external electrode is formed on the upper surface of the upper substrate,
The upper surface of the lower substrate is joined to the lower surface of the pedestal portion, and a gap is formed between the lower surface of the weight body and the upper surface of the lower substrate,
An acceleration / angular velocity sensor, wherein a container is constituted by the upper substrate, the pedestal portion, and the lower substrate, and a supporting means is constituted by the flexible portion. The sensor according to claim 13,
An acceleration / angular velocity sensor, wherein the intermediate substrate is made of a conductive material, and wiring of a detection circuit for the displacement electrode is performed via a pedestal portion. The sensor according to claim 13 or 14,
An acceleration / angular velocity sensor, wherein a groove for forming a thin portion having a small thickness is formed on an upper surface of an upper substrate, and an external electrode is formed on a bottom surface of the groove. The sensor according to claim 15,
An acceleration / angular velocity sensor characterized in that a reinforcing material is filled in a groove in which an external electrode is formed. The sensor according to any one of claims 1 to 16,
In order for the detection circuit to detect the capacitance between the displacement electrode and the external electrode,
An AC power supply that supplies an AC signal for detection having a frequency that does not match the physical resonance frequency of the weight body to one electrode;
A detection circuit for detecting an amplitude component of an AC signal generated at the other electrode;
An acceleration / angular velocity sensor characterized by comprising: The sensor according to any one of claims 1 to 16,
In order for the detection circuit to detect the capacitance between the displacement electrode and the external electrode,
A potential fixing means for fixing the potential of one of the electrodes;
An AC power supply for supplying an AC signal for detection having a frequency not matching the physical resonance frequency of the weight body to the other electrode via a resistance element;
Phase detection means for detecting the phase of an AC signal generated at the other electrode;
An acceleration / angular velocity sensor characterized by comprising: A method for manufacturing the sensor according to claim 13, comprising:
Forming a through-hole penetrating front and back at a predetermined location of the silicon substrate;
Bonding an insulating substrate to the lower surface of the silicon substrate;
Polishing the lower surface of the insulating substrate until a predetermined thickness is obtained;
Forming an insulating film on the upper surface of the silicon substrate;
Forming a conductive layer on the upper surface of the insulating film and the groove formed by the through hole;
Patterning the conductive layer to form an external electrode located at the bottom of the groove and a wiring for the external electrode;
To manufacture an upper substrate having a two-layer structure of the silicon substrate and the insulating substrate and having an external electrode formed thereon. In the manufacturing method of the sensor according to claim 19,
A method of manufacturing an acceleration / angular velocity sensor, further comprising a step of filling a groove with a reinforcing material after patterning the conductive layer. In the manufacturing method of the sensor according to claim 19 or 20,
The step of forming a through-hole in the silicon substrate is performed by anisotropic etching so that a tapered through-hole that extends upward is formed,
Prepare a glass substrate as an insulating substrate, and perform anodic bonding between the silicon substrate and the glass substrate,
A method of manufacturing an acceleration / angular velocity sensor, comprising: forming an insulating film on an upper surface of a silicon substrate by forming an insulating film made of silicon oxide by oxidizing a silicon surface.