JPH11271354A - Capacitive sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor of a capacitance detection type which is highly accurate and can be manufactured in a simpler process than conventionally. SOLUTION: In this capacitive sensor, a metallic wiring which works as a connection circuit to a movable part (vibration mass 200) for detecting an acceleration, a pressure, an angular velocity, etc., is not arranged on a thin beam as in the prior art. The sensor is provided with capacitances 220, 221 not changed in capacity by a shift while the movable part is set as one electrode, thereby outputting a signal corresponding to the shift by an a.c. signal via the capacitances. Since a series equivalent resistor does not pass the ultrathin metallic wiring on the thin beam and can be restricted to be considerably low, the sensor is improved in sensitivity. Moreover, the need for providing the metallic wiring on the thin beam is eliminated, so that a manufacture process for the sensor is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitive sensor of the capacitance detection type utilizing semiconductor technology, and realizes, for example, a high-sensitivity, high-precision capacitive angular velocity sensor, angular velocity sensor, pressure sensor, etc. at low cost. Related to technology.

[0002]

2. Description of the Related Art As an example of a conventional capacitive sensor, there is an angular velocity sensor disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 5-31576. FIG. 10 is a schematic plan view of the above conventional example. The sensor of FIG. 10 supports a vibrating mass (100) with beams arranged in the X and Y axis directions on a Si semiconductor substrate, vibrates in the X direction, and generates Coriolis force generated in the Y axis direction by angular velocity around the Z axis. , Y-axis direction. Displacement detection in the Y-axis direction is performed by providing an electrode (101) and an electrode (102) and an electrode (101) and an electrode (105) opposed to each other, and changing a distance between the electrodes to change a capacitance. Detect based on
In addition, in Japanese Patent Application Laid-Open No. 5-322576, only one electrode (101) and (102) is described, but in principle, two opposed electrodes are provided as shown in FIG.
You may detect as a differential capacitance of both. Also, a comb-shaped electrode is used to increase the capacitance between the electrodes and improve the sensitivity.

Generally, the Coriolis force generated by the angular velocity is very small, so that the vibrating mass (10
In order to displace 0), the oscillating mass (100) is made heavy, the spring constant of the beam supporting the oscillating mass (100) is reduced, or the distance between the electrodes of the capacitance for detecting (for example, 101 and 1)
It is desirable to shorten the distance between the two. In this conventional example, in order to make the vibrating mass (100) relatively large and reduce the spring constant of the beam supporting the vibrating mass (100),
The beam is thin and long. And a detection electrode (101),
(102) and (105) are provided on the beam, and external terminals (10) are provided therefrom by metal wiring such as Al provided on the semiconductor substrate.
3), (104) and (106).

[0004]

As described above, conventionally,
A signal is extracted from a detection electrode provided on the vibrating mass to a detection circuit formed on the semiconductor substrate by using metal wiring. Therefore, as shown in FIG. 10, it is necessary to form the metal wiring on a thin beam, which causes the following problem.

First, when miniaturization is performed to improve sensitivity, there is a problem that it is difficult to form metal wiring on beams. In order to increase the sensitivity of the capacitive sensor, it is effective to reduce the spring constant of the beam to increase the displacement. Generally, the spring constant k of a doubly-supported beam fixed at both ends is represented by B, Assuming that the width is b, the thickness is h, and the Young's modulus is E, it is expressed by the following (Equation 1).

K = (16 · E · b · h ³ ) / B ³ (Equation 1) Therefore, in order to reduce k, the width b and thickness h of the beam may be reduced and the length B may be increased. . However, considering the miniaturization of the sensor, it is more effective to reduce the width b of the beam than to increase the length B of the beam. Therefore, in order to realize a small and highly sensitive sensor, the width of the beam may be several μm or less in some cases. It is very difficult to form metal wiring on the beam due to restrictions such as wiring patterning.

Further, when the metal wiring is thin as described above, there is a problem that the sensitivity is reduced. In other words, when the sensor is miniaturized and the beam is made thinner in order to increase the sensitivity, the metal wiring provided on the beam needs to be made thinner, so that the electric resistance of the metal wiring increases. When the electrical resistance increases, the electrical sharpness Q of the LCR resonance circuit decreases. That is, if the resistance of the metal wiring is R, the inductance is L, and the capacitance between the electrodes is C, the sharpness Q is expressed by the following equation (2). Become smaller. Q = ωL / R = 1 / ωCR = (1 / R) · [√ (L / C)] (2) Obtaining an output using an LCR resonance circuit with a capacitive sensor is a large output at a resonance point. Using the capacitance change Δ
Since C is amplified and detected, if the electrical sharpness Q decreases as the resistance R of the metal wiring increases as described above, the sensitivity decreases.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art as described above, and provides a capacitive sensor which has high sensitivity, high accuracy, and can be manufactured by a simpler process than the conventional one. The purpose is to provide.

[0009]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, according to the first aspect of the present invention, the movable portion is formed as one electrode as a circuit for connection to the movable portion supported by the fixed portion via a beam so as to be displaceable, and the movable portion is displaced. The configuration is such that the second inter-electrode capacitance, which does not change even when the capacitance is changed, is used. As described above, in the present invention, instead of providing a metal wire on a thin beam as in the related art as a connection circuit to the movable portion, the movable portion is used as one electrode, and an electrostatic capacitor whose capacitance does not change due to displacement is used. A capacitance is formed, and a signal corresponding to the displacement is output by an AC signal through the capacitance. Therefore, the series equivalent resistance can be kept extremely low, thereby improving the sensitivity. In addition, since it is not necessary to provide a metal wiring on a thin beam, the manufacturing process is facilitated. This configuration corresponds to, for example, first to fourth embodiments described later.

[0010] The invention described in claim 2 is the same as the claim 1.
1 shows a configuration when the invention described in (1) is applied to an angular velocity sensor. This configuration corresponds to, for example, first to fourth embodiments described later.

[0011] The invention according to claim 3 is that the movable part is used as the capacitor (the second interelectrode capacitance according to claim 1 or the third capacitance according to claim 2) used as the connection circuit. A capacitance composed of an electrode provided in parallel with the main surface of the substrate from the oscillating mass and an electrode fixed to the substrate and arranged in parallel with the electrode is provided at both ends of the oscillating mass. Capacitance changes due to displacement are provided so as to be complementary to each other, and by connecting the two capacitors in parallel, a change in capacitance according to the displacement of the vibrating mass in the first direction and the second direction is obtained. It is configured so as to offset each other and not change as a whole. Note that the above configuration corresponds to, for example, a first embodiment described later.

The invention according to a fourth aspect is characterized in that the substrate used as the connection circuit (the second inter-electrode capacitance according to the first aspect or the third capacitance according to the second aspect) is used as the substrate. Part of the projecting in the direction of the vibrating mass to become the movable portion, or the capacitance formed between the electrode and the vibrating mass formed so as to face the vibrating mass, or
A part of the lid formed on the side opposite to the substrate is projected in the direction of the vibrating mass, or the capacitance formed between the electrode and the vibrating mass formed so as to face the vibrating mass, or , The above two are connected in parallel. Note that the above configuration corresponds to, for example, the second to fourth embodiments described later.

According to a fifth aspect of the present invention, the opposing area between the electrode formed by projecting a part of the substrate and the electrode formed by projecting a part of the lid and the vibrating mass is: It is installed at a position smaller than the area of the vibrating mass and where the facing area between the electrode and the vibrating mass does not change even if the vibrating mass is displaced. With such a configuration, the capacitance does not change even if the vibrating mass is displaced, and can be used as a simple connection circuit. This configuration corresponds to, for example, the second to fourth embodiments described later.

The invention according to claim 6 uses an LCR resonance circuit as means for detecting a change in the first inter-electrode capacitance whose capacitance changes in accordance with the displacement of the movable portion. . This configuration corresponds to, for example, first to fourth embodiments described later.

[0015]

As described above, according to the present invention, the wiring is not provided on the thin beam, and the vibrating mass is connected in an alternating manner by the capacitance, so that the series equivalent resistance can be extremely suppressed. Yes, thereby improving sensitivity.

Further, even if the beam is made thinner to reduce the spring constant of the beam, the sensitivity of the detection circuit does not decrease, so that a small and highly sensitive sensor can be realized.

Further, since the beam and the vibrating mass are made of a single member and no dissimilar materials such as metal wiring are used at all, adverse effects such as deterioration of temperature characteristics due to the use of dissimilar members as in the conventional example are given. There is no. In addition, since movable structures such as beams and vibrating masses are of the same thickness and made of the same material,
A vibration mode as designed can be realized, and a highly accurate sensor can be realized.

Further, since no metal wiring or the like exists on the beam, the beam can be formed by a relatively simple process.
In addition, since there is no need to consider wiring and the like, various effects can be obtained, such as the width of the beam can be reduced to the process limit, and a highly sensitive sensor can be realized at a low cost by a simple manufacturing process.

[0019]

(First Embodiment) FIG. 1 is a diagram showing a structure of a first embodiment according to the present invention.
(A) is a perspective view, and (b) is an AA ′ cross-sectional view of (a). This embodiment illustrates a case where the present invention is applied to a vibration type angular velocity sensor. The angular velocity sensor is a semiconductor Si
It is formed on the surface through a relatively thick insulating layer (231) formed on the substrate (230). That is, the vibrating mass (200) made of Si is connected to the truss portions (212) provided on both sides by four detection beams (211) extending in parallel to the substrate in the X direction, and is separated from the insulating layer (231) by a predetermined amount. Floating in the air with a small spacing. From the two trusses (212), a total of eight drive beams (210) parallel to the substrate extend in the Y-axis direction, and are connected to four common fixed electrodes (203) fixed to the substrate. .

In the vibrating mass (200), the comb-like electrodes for detection extend in parallel with the X direction, and the combs for opposed detection extend from the fixed electrodes for detection (201) and (202) fixed to the substrate. It is arranged at a predetermined interval from the tooth-shaped electrode, and forms capacitances (222) and (223).
At this time, the plurality of comb electrodes forming the capacitance are arranged at different intervals, and the capacitances (222) and (223)
And are in a different order. That is, the capacitance (22
The interval between the comb electrodes forming 2) is narrower when the fixed electrode for detection (201) is on the upper side (positive direction of the Y axis), and the comb electrodes forming the capacitance (223) are 20
The interval is narrower when the 0) side is at the top. Therefore,
For example, when the vibrating mass (200) is slightly displaced upward (positive Y-axis direction) on the plane of the drawing, the capacitance (222) increases because the interval between the comb-teeth electrodes becomes narrower, and the other capacitance increases. (223) is reduced. If the amount of displacement is smaller than the initial distance between the electrodes, the change between the amount of displacement and the capacitance value becomes linear, and the capacitance values (222) and (223) complementarily change. become. In the capacitances (222) and (223), the comb-teeth electrode on the vibrating mass side extends from both sides in the X-axis direction (left and right sides in the figure) with respect to the comb-teeth electrode on the fixed electrode side for detection. Oscillating mass (2
00) is displaced in the X-axis direction, there is no change in the amount of overlap between the detection electrodes. Therefore, there is no change in these detection capacitances (222) and (223). That is, Y
Only axial displacement is detected.

Similarly, from the vibrating mass (200), in order to form a coupling capacitance different from the above-described detection capacitance, a coupling comb electrode is formed parallel to the substrate in the X-axis direction. Fixed electrode for coupling (206),
The fixed comb-teeth electrode for opposing coupling extending from (207) is arranged at a predetermined interval, and the capacitance (22
0) and (221). At this time, the comb electrodes forming the capacitance are arranged at different intervals, and the order of the capacitances (220) and (221) is different. That is, the distance between the comb electrodes forming the capacitance (220) is narrower when the coupling fixed electrode (206) is on the upper side (Y-axis positive direction), and the capacitance (221) is smaller.
Are narrower when the vibrating mass (200) side is on the upper side. Therefore, the oscillating mass (20
For example, when (0) is slightly displaced in the upward direction (positive Y-axis direction) on the paper surface, the capacitance (220) increases because the interval between the comb-teeth electrodes becomes narrower, and the other capacitance (221) increases.
Decreases. If the displacement in the Y-axis direction is smaller than the initial gap between the electrodes, the displacement and the change in the capacitance value are linear, and the capacitance is complementary to the capacitances (220) and (221). The change is similar to the detection capacitances (222) and (223). However, in the capacitances (220) and (221), the amount of overlap of the comb electrode changes even when the vibrating mass (200) is displaced in the X-axis direction.
0) and (221) change complementarily. At this time, since the change of the capacitances (220) and (221) is proportional to the amount of overlap of the electrodes, even if the amount of displacement in the X-axis direction is large, the linearity of the amount of displacement and the change of the capacitance value is large. Is kept.

Further, from the truss portion (212), driving comb electrodes are formed in the X-axis direction parallel to the substrate.
From the fixed electrodes for driving (204) and (205), X
A fixed comb-teeth electrode for opposing drive extending in parallel with the substrate in the axial direction is arranged at a predetermined interval to form a capacitance.

These oscillating masses (20
0), the detection beam (211), the truss portion (212), the driving beam (210), the fixed electrodes (201) to (207), and the comb-tooth electrode are all made of the same material and have the same thickness. [Refer to the sectional view of FIG. 1 (b)]. Each of the electrodes (201) to (207) is a metal electrode for connection to the outside, and can be electrically connected to the outside freely by ordinary wire bonding. What is characteristic here is that, unlike the conventional example, there is no dissimilar member (metal wiring or the like) on the vibrating mass or the beam supporting it, and it is formed of a single semiconductor Si material.

Each of the metal electrodes (201) to (207)
In order to make ohmic contact with the underlying semiconductor Si, high-concentration impurity diffusion may be performed below each metal electrode, but is not shown in the present embodiment.

Next, FIG. 2 is an electrical connection diagram for taking out a small change in the detection capacitances (222) and (223) in the present embodiment, and FIG. 3 is an equivalent circuit diagram thereof. It is. In FIG. 2, an AC power supply for detection (Vs) is connected to a fixed electrode for detection (201), and the other fixed electrode for detection (202) is grounded. The fixed electrodes for coupling (206) and (207) are commonly connected externally, and an inductor (3) is used to form an LCR resonance circuit.
00). That is, the coupling capacity (22
0) and (221) are connected in parallel. The other end of the inductor (300) is grounded. On the other hand, semiconductor S
The potential of the i-substrate (230) is externally connected to the common fixed electrode (203) via the back surface of the substrate, and the movable mass (200), the truss (212), etc. are connected to the substrate (23).
0) is maintained at the same potential. In addition, as the angular velocity sensor, an alternating voltage is applied between the driving fixed electrodes (204) and (205) and the common fixed electrode (203), and the vibrating mass (200), the detection beam (211) and the truss unit are used. (21
2) needs to be vibrated (displaced) in the X-axis direction, but since this portion is the same as the conventional one, it is omitted for simplification.

Next, in the equivalent circuit shown in FIG.
(Corresponding to the capacitance 222) and C2 (corresponding to the capacitance 223) are detection capacitances that change complementarily in the Y-axis direction as described above. Cc1 (corresponding to the capacitance 220) and Cc2 (corresponding to the capacitance 221) are coupling capacitances that also change complementarily in the Y-axis direction.
Since the two are connected in parallel, the oscillating mass (20
0) The capacitance is always constant regardless of the movement in the X and Y directions. L is the inductance of the inductor (300), RL is the series equivalent resistance of the inductor (300), Rb is the equivalent resistance of the beam, and Rs is the distributed equivalent resistance of the vibrating mass (200) (both are electrical resistances). .

Cs1, Cs2 and Cs3 are stray capacitances between the substrate, the fixed electrodes for detection (201) and (202) and the vibrating mass (200), respectively. In this angular velocity sensor, the insulating layer (231) is relatively thick in order to increase the capacitance change rate of each comb-tooth electrode caused by the movement in the XY plane and to improve the sensitivity.
These stray capacitances Cs1, Cs2, Cs3 are equal to the detection capacitance C
1, C2 and the coupling capacitances Cc1 and Cc2 are small values.

Next, the operation of the first embodiment will be described. As described above, the fixed electrode for coupling (20
6), Cc1 (capacitance 220) and Cc2 (capacitance 221) formed by the comb-teeth electrodes of (207) and the vibrating mass (200) have the vibrating mass (200) displaced in the Y-axis direction. In both cases and when displaced in the X-axis direction, they change complementarily. Therefore, even if the oscillating mass (200) is displaced in the X-axis direction or the Y-axis direction due to the application of the driving signal or the application of the angular velocity, one capacitance value decreases in accordance with the displacement, and the other capacitance value decreases. The capacitance value increases, and both change complementarily. Therefore, if Cc1 and Cc2 are connected in parallel, the total capacitance value is the sum of the two, and the total capacitance value does not always change. That is, the combined capacitance value obtained by connecting Cc1 and Cc2 in parallel does not always change when the vibrating mass (200) is displaced in either the Y-axis direction or the X-axis direction, and the fixed capacitance value is fixed to that portion. The circuit works in the same way as a capacitor is connected, and electrically serves as a circuit for passing an AC signal.

In the above configuration, the oscillating mass (200) and the detection beam (211) are applied by an AC voltage (not shown) applied to the fixed electrodes for driving (204) and (205).
It is assumed that the truss portion (212) is vibrating in the X-axis direction. Here, when an angular velocity is applied around the Z-axis, Coriolis force is generated in the vibrating mass (100), and vibration also starts in the Y-axis direction. The displacement in the Y-axis direction is the detection capacitance C.
Although the difference between 1 and C2 is obtained, the output is multiplied by Q (Q is the sharpness of the LCR resonance circuit) by forming an LCR resonance circuit as shown in FIG. The change ΔVout of the output voltage at the node (301) is as shown in the following equation (3).

ΔVout = (Vs · Q · ΔC) / (2 · C0) (3) where Vs: applied AC voltage C0: capacitance when there is no displacement (C1 = C2 = C0) Δ C: Change in capacitance (C1 = C0 + ΔC, C2 = C0−
ΔC) In the equation (3), Vs is an alternating current, so that the output voltage Vout is also an alternating current, so that it can be taken out through a parallel capacitance of Cc1 and Cc2.

The electric resonance frequency fr is expressed by the following equation (4) and is constant irrespective of mechanical vibration. fr
= 1 / {2π ×} [L (C1 + C2 + Cc1 + Cc
2)]｝ (Equation 4) The vibrating mass (2
00) and the truss portion (212) are at the same potential as the semiconductor Si substrate (230), so that no electrostatic attraction occurs between them and the movable portion does not stick to the substrate.

As described above, in the first embodiment, as shown in an equivalent circuit diagram of FIG.
The signal corresponding to the angular velocity detected as the change of 2 is taken out through the coupling capacitors Cc1 and Cc2 connected in parallel and the coupling fixed electrodes (206) and (207). Therefore, there is no need to provide a metal electrode for signal detection on the thin beam supporting the vibrating mass (200).

Hereinafter, effects of the first embodiment will be described. The sharpness Q of the LCR resonance circuit depends on the series equivalent resistance R existing in the resonance circuit as shown in the above equation (2). Therefore, as R increases, Q decreases, and the sensitivity decreases as can be seen from equation (3). However, in the present embodiment, no wiring is provided on the thin beam, the vibrating mass (200) is connected in an alternating manner by the coupling capacitances Cc1 and Cc2, and the metal wiring is a coupling capable of forming a thick wiring. Fixed electrode (206),
(207). Therefore, the series equivalent resistance can be kept extremely low, thereby improving the sensitivity.

Furthermore, even if the beam is made thinner to increase the sensitivity and lower the spring constant of the beam, the electric resistance (R
Although b) increases, since it is unrelated to the LCR resonance circuit, there is no sensitivity reduction in the detection circuit.

Further, when a metal wiring is provided on a beam as in the conventional example, there is a difference in the thermal expansion coefficient between different kinds of members such as metal and Si. Distortion changes occur in the mass, causing offset and sensitivity to change. In particular, in order to route such metal wirings having different potentials, it is necessary to insulate the metal wiring from the underlying semiconductor Si substrate. For example, it is necessary to form a Si oxide film or the like on the surface of the beam or the vibrating mass. However, if a different member such as an insulating film is formed on the beam or the vibrating mass, the temperature characteristics deteriorate due to the difference in the thermal expansion coefficient. In this regard, in this embodiment, since the beam and the vibrating mass are made of a single member, and no extra dissimilar material is used, deterioration of temperature characteristics due to the use of dissimilar members as in the conventional example, etc. No adverse effects.

Further, when a metal or the like having a density different from that of Si is partially formed on the beam or the vibrating mass as in the conventional example, the balance between the vibrating mass and the beam is lost. In particular, in the case of a sensor that performs high-precision vibration / detection on the XY plane as in the conventional example, high-order vibrations other than the primary mode in the X and Y directions are induced, which adversely affects the sensor characteristics. That point,
In the present embodiment, since the movable structures such as the beam and the vibrating mass have the same thickness and are made of the same material, a vibration mode as designed can be realized, and a highly accurate sensor can be realized.

Further, even if the electrodes forming the capacitance are to be formed as in the conventional example, it is difficult to secure the facing area. For example, the electrodes (101) and (102) of FIG.
Must have a thickness perpendicular to the paper,
It is very difficult to selectively form metal electrodes in the thickness direction of the Si structure. Ideally, if the electrodes can be formed fully in the thickness direction of the structure Si, the facing area can be effectively secured.However, in a normal semiconductor process, in general, a patterned electrode is formed on a surface perpendicular to the substrate. It is very difficult to form. In this regard, in the present embodiment, since there is no metal wiring or the like on the beam, the beam can be formed by a relatively simple process. The sensor can be narrowed to the limit, and a highly sensitive sensor can be realized.

Next, a method of manufacturing the device shown in the first embodiment will be described. FIGS. 4A to 4E are cross-sectional views illustrating an example of a manufacturing process according to the first embodiment. First, as shown in (a), a semiconductor Si substrate (23
0) Deposit a relatively thick insulating layer (231) on top. In order to increase the sensitivity by reducing the above-mentioned stray capacitances Cs1, Cs2, Cs3, for example, the thickness of the insulating layer (231) is set to several tens to several hundreds μm. Usually, in semiconductor processes such as CVD,
Although it is difficult to deposit a relatively thick insulating layer, for example, a soot method for depositing boron glass thickly can be used.
Also, after bonding the glass substrate to the Si substrate by anodic bonding, etc.,
The insulating layer (glass in this case) may be ground or etched / polished to a predetermined thickness.

Next, as shown in FIG.
1) A Si substrate (400) is bonded on top. This method may be an anodic bonding method or a high-temperature bonding method. Next, (c)
As shown in the Si substrate (400) adhered to ground or etched to a predetermined thickness, after grinding, SiO ₂
Using a mask such as described above, trench etching is performed in a predetermined pattern to pattern Si.

Next, as shown in (d), the insulating layer (23)
The so-called sacrifice layer etching, in which 1) dissolves, for example, etching the portion of the insulating layer (231) from the above-described patterned hole using a solution such as HF, is performed. Part (vibration mass 200
And so on). Next, as shown in FIG.
Are formed on necessary fixing parts by using, for example, a shadow mask method.

In the above example, the sacrifice layer etching method is used as a method of forming the movable portion. However, a portion to be a gap may be formed in advance on the insulating layer of the substrate, and then bonded and etched. . Also, the formation of the Al electrode in the step (e) may be performed in advance in the step (c), and in a subsequent process, the Al film may be protected by a protective film so that the Al is not etched.
In any case, in the structure of the present embodiment, since the movable portion itself is used as an electrode, the structure can be compared without forming an Al electrode on the side surface of the structure or forming an insulating film on the structure. The sensor can be easily manufactured.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
It is a diagram showing the structure of the embodiment of the present invention, (a) is a perspective view,
(B) shows an AA ′ cross-sectional view of (a). In this embodiment, the oscillating mass, beam, truss portion, detection electrode, drive electrode, and the like are the same as those in the first embodiment, and thus description thereof will be omitted. This embodiment differs from the first embodiment in that a coupling capacitance is formed between the semiconductor Si substrate (230) and the vibrating mass.

In FIG. 5, the coupling electrode (50
0) opposes the oscillating mass (200) at a small interval, so that the insulating layer (23) is removed from the semiconductor Si substrate (230).
The coupling capacitance (501) is formed between the coupling electrode (500) and the vibrating mass (200). At this time, the planar size of the coupling electrode (500) is a size included in the opposing surface of the vibrating mass (200),
Even if the oscillating mass (200) moves on the XY plane, the opposing areas are set so as not to change. Therefore, even if displacement of the vibrating mass (200) in the X-axis direction due to driving of an AC voltage or displacement in the Y-axis direction due to application of angular velocity occurs, the value of the coupling capacitance (501) does not change.

Coupling electrode (500) as described above
The coupling capacitances (220) and (221) in FIG. 1 and the coupling fixed electrode (2) in FIG.
06) and (207) are not provided. Other structures are the same as those in FIG.

FIG. 6 is an equivalent circuit diagram of the sensor of FIG. In FIG. 5, Cc3 is the coupling capacitance (501). The difference from the first embodiment is that the coupling capacitance (Cc3) is formed by the coupling electrode (500) extending from the semiconductor Si substrate (230), and the oscillating mass (200) passes through the coupling capacitance Cc3. The point is that it is capacitively coupled directly to the semiconductor Si substrate (230).

Next, the operation of the second embodiment will be described. As described above, even if displacement in the X-axis direction due to driving of an AC voltage or displacement in the Y-axis direction due to application of angular velocity occurs in the oscillating mass (200), the coupling capacitance (501) does not change. Therefore, the coupling capacitance (501) acts as if a fixed capacitance is connected, and becomes a circuit that electrically passes an AC signal. Therefore,
Since the oscillating mass (200) is connected to the semiconductor Si substrate via the coupling capacitance (501),
It is not necessary to form metal wiring for connecting to the vibrating mass (200) on a thin beam. Other functions are the first
This is the same as the embodiment.

Next, effects of the second embodiment will be described. The main effects of the second embodiment are the same as those of the first embodiment, but the magnitude of the capacitance is proportional to the area. In some cases, providing the electrode on the surface of the oscillating mass (200) having a larger area than the comb-shaped electrode as in the first embodiment can increase the area. For this reason, there is an advantage that the coupling capacity is larger than that of the first embodiment and can be easily obtained depending on design conditions. Further, since there is no portion protruding in the X direction unlike the first embodiment, the size in the XY two-dimensional plane may be smaller than that of the first embodiment.

Next, a method of manufacturing the device shown in the second embodiment will be described. FIG. 7 (x), (y), (b)
(E) is sectional drawing which shows an example of the manufacturing process in 2nd Embodiment. First, as shown in (x), the semiconductor Si substrate (230) is etched to form a convex portion (232) which will later become the coupling electrode (500). Next, as shown in (y), an insulating layer (231) is formed on the entire surface, and the surface is flattened. The thickness of the insulating layer (231) is larger than the thickness of the convex portion (232) by the thickness of the sacrificial layer.

Hereinafter, the steps (b) to (e) are performed in the first
Is the same as that of the first embodiment, but when the sacrificial layer is etched in the step (d), the insulating layer (2) on the convex portion (232) is formed.
31) is completely etched away, and the convex portion (232) is removed.
Should appear on the surface.

(Third Embodiment) FIG. 8 is a sectional view showing a structure of a third embodiment of the present invention. In the third embodiment, a lid (700) made of a semiconductor material, glass, or the like is provided above the sensor substrate, and the lid (70) is formed.
The coupling electrode (701) is arranged near the upper portion of the vibrating mass (200) in (0), and a coupling capacitance (702) is formed between the coupling electrode (701) and the vibrating mass (200). At this time, the size of the coupling electrode (701) is
The size is included in the facing surface of the vibrating mass (200). Thereby, even if the oscillating mass (200) moves on the XY plane, the facing area does not change and the coupling capacity (70)
2) is not changed. When the lid (700) is made of a semiconductor material such as Si, the coupling electrode (701) may be used in a convex shape, or the lid (700) may be made of an insulating material such as glass. In this case, an electrode such as a metal film may be formed on the portion. The operation of the third embodiment is the same as that of the first and second embodiments.

Next, the effect of the third embodiment will be described. The main effects of the third embodiment are the same as those of the first and second embodiments, except that the semiconductor Si substrate (230) is not processed as in the second embodiment, and Since the coupling electrode (701) may be formed on (700), the process may be simpler than processing the substrate. In particular, in the case of such a vibration type sensor, the third embodiment has the advantage that operating under reduced pressure can increase the mechanical Q value rather than operating in the atmosphere. It may be necessary to form an airtight lid such as In such a case,
If the coupling electrode (701) is formed at the same time when the lid is processed, it can be easily manufactured.

Although the details of the method of manufacturing the element described in the third embodiment are omitted, the processing of the lid and the formation of the electrodes can be easily performed by using a general semiconductor process. .

(Fourth Embodiment) FIG. 9 is a sectional view showing a structure of a fourth embodiment of the present invention. This embodiment is a combination of the second and third embodiments. The semiconductor Si substrate (230) is also provided with a coupling electrode (500) having a convex shape, and the lid (70) is provided.
0) is also provided with a coupling electrode (701) so that the vibrating mass (200) is vertically sandwiched between them.

Next, the operation of the fourth embodiment will be described. In the fourth embodiment, the oscillating mass (200) is vertically sandwiched between the coupling electrode (500) and the coupling electrode (701) to form coupling capacitors (501) and (702), respectively. doing. When the oscillating mass (200) is slightly displaced in the Z-axis direction, the two coupling capacitances complementarily change when one increases and the other decreases. Therefore, if the two coupling capacitances (501) and (702) are connected in parallel, the total coupling capacitance value will be as follows even if the oscillating mass (200) is displaced in the Z-axis direction and the displacement is small. It does not change. Therefore, even when the oscillating mass (200) is displaced in the Z-axis direction, which is not normally displaced, there is no possibility that an extra noise component is transmitted to the output. Note that the device described in the fourth embodiment can be realized by the same manufacturing method as in the second and third embodiments.

In the above embodiments,
Although the angular velocity sensor has been described as an example, the present invention can be similarly applied to a pressure sensor and an acceleration sensor.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing a structure according to a first embodiment of the present invention, wherein FIG. 1A is a perspective view, and FIG. 1B is a cross-sectional view taken along line AA ′ of FIG.

FIG. 2 is a circuit diagram according to the first embodiment;

FIG. 3 is an equivalent circuit diagram of the first embodiment.

FIG. 4 is a cross-sectional view showing a step of manufacturing the element shown in the first embodiment.

FIGS. 5A and 5B are diagrams showing a structure according to a second embodiment of the present invention, in which FIG. 5A is a perspective view, and FIG. 5B is a sectional view taken along line AA ′ of FIG.

FIG. 6 is an equivalent circuit diagram of the second embodiment.

FIG. 7 is a cross-sectional view showing a step of manufacturing the element shown in the second embodiment.

FIG. 8 is a sectional view showing a structure according to a third embodiment of the present invention.

FIG. 9 is a sectional view showing a structure according to a fourth embodiment of the present invention.

FIG. 10 is a plan view showing the structure of a conventional example.

[Explanation of symbols]

100: Vibration mass 101, 10
2, 105 detection electrodes 103, 104, 106 external terminals 200 vibration mass 201, 202 detection fixed electrodes 203 common common electrodes 204, 205 driving fixed electrodes 206, 207 coupling fixed electrodes 210 Driving beam 211: Detection beam 212: Truss 220, 221
... Coupling capacitance 222, 223 ... Capacitance 230 ... Semiconductor Si substrate 231 ... Insulating layer 232 ... Convex part 300 ... Inductor 301 ... Output terminal 400 ... Si substrate 500 ... Coupling electrode 501 ... Coupling capacitance 700 ... Lid 701: Coupling electrode 702: Coupling capacitance Vs: AC power supply for detection C1, C2: Detection capacitance Cc1, Cc2: Coupling capacitance Cs1, Cs
2, Cs3: stray capacitance L: inductance of inductor RL: series equivalent resistance of inductor Rb: equivalent resistance of beam Rs: distribution equivalent resistance of oscillating mass

Claims (6)

[Claims] A movable portion supported by a fixed portion via a beam so as to be displaceable; and a first electrode having the movable portion formed as one electrode and having a capacitance that changes according to the displacement of the movable portion. And a second inter-electrode capacitance in which the movable portion is formed as one electrode and the capacitance does not change even if the movable portion is displaced. And a signal corresponding to a change in the first inter-electrode capacitance is output to a processing circuit formed in the fixed unit via the first sensor. 2. A vibrating mass formed as a movable portion formed on a flat substrate at a small interval and supporting a vibrating mass formed such that the vibrating mass can vibrate in parallel with the main surface of the substrate. A beam, excitation drive means for vibrating the vibrating mass in a first direction parallel to the main surface of the substrate, and a rotation axis in a third direction perpendicular to the main surface of the substrate.
Displacement of the vibrating mass in the second direction caused by Coriolis force generated in a second direction parallel to the main surface of the substrate and perpendicular to the first direction is caused by a capacitance formed by using the vibrating mass as one electrode. A capacitive sensor that detects an angular velocity applied in the rotational direction by detecting a change in the value; a first electrode extending in a first direction parallel to the main surface of the substrate from the vibrating mass; A first detection capacitor, which comprises a second electrode fixed and disposed in parallel with and opposed to the first electrode, wherein a capacitance value changes according to a displacement of the vibrating mass in a second direction; A second detection capacitor having the same shape as the first detection capacitor and arranged at a line symmetric position with respect to the first direction; and the vibrating mass itself or an electrode provided thereon as one electrode, Third electrode fixed to the substrate A third capacitance formed as the other electrode, wherein the third capacitance does not change in capacitance value due to displacement of the vibrating mass in the first direction and the second direction; An AC voltage is applied between the electrode fixed to the substrate of the second detection capacitor and the electrode fixed to the substrate of the second detection capacitor, and the electrode is fixed to the substrate of the third capacitance. By connecting an inductance to the third electrode, an electric LCR resonance circuit is formed.
The capacitive sensor according to claim 1, wherein a displacement of the vibrating mass in the second direction is measured by measuring a voltage of a connection node between the electrode and the inductance. 3. The second inter-electrode capacitance according to claim 1 or the third capacitance according to claim 2 extends from the vibrating mass serving as the movable portion in a first direction parallel to the main surface of the substrate. A fourth electrode fixed to the substrate and the fourth electrode
A fourth capacitance, which comprises a fifth electrode disposed in parallel with and opposed to the fifth electrode, and a capacitance value of which changes in accordance with displacement of the vibrating mass in the first direction and the second direction; A fifth capacitor, which has the same shape as the fourth capacitor, is disposed at a position opposite to the vibrating mass with respect to the second direction, and has a capacitance value that complementarily changes with the fourth capacitor; The second capacitor is connected in parallel by electrically short-circuiting the electrode of the fourth capacitor fixed to the substrate and the electrode of the fifth capacitor fixed to the substrate. 2. The configuration according to claim 1, wherein a change in the capacitance according to the displacement of the vibrating mass in the first direction and the second direction is offset, and the capacitance is not changed as a whole. Alternatively, the capacitive sensor according to claim 2. 4. The second inter-electrode capacitance according to claim 1 or the third capacitance according to claim 2, wherein a part of the substrate protrudes in a direction of the vibrating mass serving as the movable portion. Either an electrostatic capacitance formed between the vibrating mass and an electrode formed so as to face the vibrating mass at a small interval, or a lid formed on the opposite side of the substrate with respect to the vibrating mass A part of the part is projected in the direction of the vibrating mass, or is the capacitance formed between the vibrating mass and an electrode formed so as to face the vibrating mass at a small interval,
Or, the capacitance formed between the electrode formed by projecting a part of the substrate and the vibrating mass, and the capacitance formed between the electrode formed by projecting a part of the lid and the vibrating mass. The capacitance type sensor according to claim 1 or 2, wherein the formed capacitance is connected in parallel. 5. An opposing area between an electrode formed by projecting a part of the substrate and an electrode formed by projecting a part of the lid and the vibrating mass is smaller than an area of the vibrating mass. 5. The capacitive sensor according to claim 4, wherein the capacitive sensor is provided at a position where the facing area between the electrode and the vibrating mass does not change even when the vibrating mass is displaced. 6. 6. A change in the first inter-electrode capacitance, the capacitance of which changes in accordance with the displacement of the movable portion, is performed by applying an AC voltage to the first inter-electrode capacitance. The capacitive sensor according to claim 1, wherein the capacitive sensor is configured to be detected as an output of an LCR resonance circuit in which an inductance is connected to a series circuit of the inter-electrode capacitance and the second inter-electrode capacitance.