JP3346379B2 - Angular velocity sensor and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor used for vibration measurement, vehicle control, motion control, and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Inertial force sensors for detecting acceleration or angular velocity applied to a moving object include a piezoelectric type, a strain gauge type, a magnetic type using a differential transformer, and a capacitance type for detecting a change in capacitance of a capacitor. There are various types.
In recent years, in particular, as an inertial force sensor that applies semiconductor micromachining technology, an acceleration sensor that uses the piezoresistance effect that changes the electrical resistance due to mechanical external force, and an acceleration that calculates the acceleration by detecting a change in the capacitance of the capacitor Sensors, and angular velocity sensors are receiving attention. These have advantages such as miniaturization, mass productivity, high precision and high reliability of the device. In particular, for an acceleration sensor that electrically detects acceleration from a change in the capacitance of a capacitor, a CAPASITIVE ACCELLEROMET
ER WITH HIGH SYMMETRICA
L DESIGN, SENSORS & ACTUAT
This technique is described in ORS, A21-A23 (1990) 312-315, and this technique will be described below with reference to FIG. Japanese Patent Application Laid-Open No. 62-93668 and U.S. Pat. No. 475 disclose an angular velocity sensor for electrically detecting the angular velocity of a rotating object from a change in the capacitance of a capacitor.
0364 and the like.

[0003] A conventional technique will be described. FIG.
ASITIVE ACCELEMETER WIT
H HIGHLY SYMMETRICAL DESI
GN, SENSORS & ACTUATORS, A2
FIG. 19 is a plan view (FIG. 19A) and a cross-sectional view taken along GG (FIG. 19B) of the acceleration sensor described in 1-A23 (1990) 312-315. In FIG. 19, 3 is a beam,
4 is a mass, 6 and 7 are fixed electrodes, 55 is a silicon substrate having the beam 3 and the mass 4, and 56 and 57 are glass substrates. The configuration and operation of this acceleration sensor will be described. This acceleration sensor includes a silicon substrate 55 including a beam 3 and a mass body 4 formed by forming a cavity by etching, a glass substrate 56 having a fixed electrode 6 attached to the surface of a groove formed by etching, and a silicon substrate 55 formed by etching. A glass substrate 57 having a fixed electrode 7 attached to the surface of the groove formed. By forming an electrode on the mass body 4 of the silicon substrate 55, the fixed electrode 6 and the mass body 4,
The fixed electrode 7 and the mass body 4 form two capacitors. By appropriately reducing the thickness of the beam 3 of the silicon substrate 55 with respect to its width, the mass body 4 of the silicon substrate 55 of the present acceleration sensor vibrates in the vertical direction when receiving acceleration in the z-axis direction. At this time, the acceleration is calculated from the change in the capacitance of the capacitor due to the displacement of the mass body 4.

Further, this acceleration sensor has a silicon substrate 55 having a beam 3 formed by forming a cavity by etching, a mass body 4, and a glass having a fixed electrode attached to the surface of a groove formed by etching. Substrate 56
And the glass substrate 57 are manufactured independently of each other,
A manufacturing process of joining these three is employed. When the beam 3 is formed on the silicon substrate 55, a very high concentration doping with a p-type impurity is performed on a portion where the beam 3 is formed. As a result, the etching rate of the portion doped with the p-type impurity is reduced. Therefore, if a very high concentration doping with a p-type impurity is performed on a portion where the beam 3 is to be formed and then the etching process is performed, the etching proceeds to a portion other than the portion where the beam 3 is formed.
Is formed.

[0005]

In the acceleration sensor described above, the capacitance of the capacitor formed by the mass 4 and the fixed electrode 6 and the capacitance formed by the mass 4 and the fixed electrode 7 due to the displacement of the mass 4 caused by the acceleration. The system detects changes.
For this reason, when the glass substrate 56, the glass substrate 57, and the silicon substrate 55 are bonded and bonded to each other, there is a problem that a residual strain is generated, and the electrode interval is different from a design value.
Another problem is that the characteristics of the acceleration sensor change due to the electrode spacing fluctuating according to the temperature change.

In the step of manufacturing the beam 3 of the silicon substrate 55, the beam 3 of the completed silicon substrate 55 is subjected to very high concentration doping of the p-type impurity in the portion where the beam 3 is formed. Causes residual strain. For this reason, the rigidity of the beam 3 is increased, and the sensitivity (displacement per 1 G:
However, G has a problem that the gravitational acceleration decreases. Also, the characteristics of the sensor fluctuate due to the fluctuation of the residual strain, and there is a problem in terms of long-term reliability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned various problems, and has a highly reliable angular velocity.
It is an object to provide a sensor and a method for manufacturing the sensor .

[0008]

SUMMARY OF THE INVENTION According to the present invention, a device (bulk micromachining technology) in which an element constituting an angular velocity sensor is formed from a pre-bonded substrate and wafer by etching is used. It relates to an angular velocity sensor . Angular velocity according to the first configuration of the present invention
Sensor includes a substrate, and bonded to the substrate, and a wafer made of monocrystalline silicon and a made structure by etching, the structure is located a gap relative to the substrate 2 Two masses, and a beam that supports each of the masses and is positioned with an air gap with respect to the substrate;
A vibrating body including an anchor supporting the beam and joining to the substrate, a vibration monitor located outside each of the mass bodies
Use fixed electrode, the fixed electrode located between said respective mass, and includes a lower fixed electrode positioned above the lower surface of the mass, wherein each mass and the movable electrode, electrically displacement of the movable electrode The angular velocity sensor according to claim 1, further comprising: an auxiliary support around the structure, and a protective substrate for sealing the structure on the auxiliary support. On the substrate, while the structure is sealed,
A groove in which each mass and the beam can freely vibrate, and a hole provided only in a portion facing the metal electrode provided in each of the anchor and each fixed electrode, and a cavity around the mass is depressurized. It was done.

According to the second configuration of the present invention,Angular velocity sensor
In the first configuration, the auxiliary support portion may be the structure body
And an electrode is provided on the auxiliary support, and an auxiliary support is provided.
The holding part is grounded.

The method for manufacturing an angular velocity sensor according to the present invention includes the following steps (1) to (4). (1) A substrate on which two lower fixed electrodes are formed and a wafer made of single-crystal silicon having a surface with a (110) crystal plane and two etching grooves are fixed to the etching grooves and the lower part. process and the electrode are joined to face, (2) is deposited back on the insulating film on the side having the etch groove of the wafer, unnecessary insulating using an etching to obtain the desired pattern on the insulating film After removing the film, the (111) of the wafer is anisotropically etched.
By etching along a plane, two mass body located with a gap with respect to the substrate, it the mass body
Supports, respectively, and a beam positioned having a gap with respect to the substrate, to support the the beams and vibrating body and a anchors bonded to the substrate, located on the outside of the respective mass Shake
Dynamic monitor fixed electrode, the fixed electrode located between said respective mass, and step (3) to form the auxiliary support section located around the structure composed of said vibrating body and the respective fixed electrodes and the anchor A step of selectively metallizing a metal electrode on each of the fixed electrodes (4) a groove in which each of the mass bodies and the beam can vibrate, and a portion facing the metal electrode provided on each of the anchor and each of the fixed electrodes; A protective board with holes only
Placed on the wafer, the protection substrate and the wafer
Anodic bonding process under reduced pressure atmosphere

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference Example 1 FIG. 1 shows a configuration of an acceleration sensor according to the present invention. FIG. 1A is a plan view of the acceleration sensor,
FIG. 1B is a cross-sectional view taken along the line AA.
FIG. 1B is a cross-sectional view when FIG. 1A is cut along the line BB.

In FIG. 1, 3 is a beam, 4 is a mass, 5 is an anchor, 6 is a fixed electrode, 7 is a fixed electrode, 8 is a metal electrode, and 9 is a substrate made of silicon. Beam 3, mass 4
And the anchor 5 are integrally formed to form a vibrating body.
Further, a structure is constituted by the vibrating body, the fixed electrode 6 and the fixed electrode 7. The structure is formed by anisotropically etching a wafer made of single-crystal silicon whose surface has a crystal face of (110) joined to the substrate 9 via an insulating film.
An electrode is formed on the vibrating body. Thereby, the mass 4
Constitutes a movable electrode that can be displaced between the fixed electrode 6 and the fixed electrode 7. The crystal plane on the side surface of the structure is composed of a (111) plane perpendicular to the crystal plane (110) plane of the wafer surface. Metal electrodes 8 are formed on the surfaces of the vibrating body, the fixed electrodes 6 and the fixed electrodes 7. The beam 3 and the mass body 4 of the vibrating body have a gap of, for example, about 2 μm to 3 μm with respect to the substrate 9, and the anchor 5
Are bonded to the substrate 9.

In order to increase the sensitivity of the acceleration sensor, it is desirable to increase only the sensitivity in a specific direction (the y direction in Reference Example 1). In order to realize this, the sensitivity in the specific direction may be designed to be sufficiently higher than the sensitivity in other directions. For this reason, the beam 3 has a high aspect (for example, w /
t <0.1). When the beam 3 has a high aspect structure, when the inertia force equal to each of the x-axis, the y-axis, and the z-axis is applied, the displacement of the mass body 4 in the z-axis direction is several tens of the displacement in the y-axis direction. It can be designed to be twice as small (for example, 1/50 or less), and the sensitivity in the z-axis direction can be designed to be very low. Also,
The displacement in the x-axis direction is defined by the compression mode or the tension mode of the beam 3, and can be made smaller than the bending mode in the z-axis direction. Therefore, it is possible to design the beam 3 to be smaller than the displacement in the z-axis direction.

The mass 4 has a parallelogram shape with an acute angle of 70.53 degrees and an obtuse angle of 109.47 degrees. The reason for such an angle is that the anisotropic etching was performed so that the crystal plane on the side surface of the structure to be formed on the wafer was formed in the (111) plane perpendicular to the (110) plane. is there.

Next, the operation of the acceleration sensor shown in FIG. 1 will be described with reference to FIG. In FIG. 2, 10 and 11 are capacitors formed by the mass body 4 and the fixed electrode 7 and between the mass body 4 and the fixed electrode 6, 12 is an AC signal source, 1
3 is an inverting amplifier, 14 is a capacitor 10 and a capacitor 1
1, 15 is a charge amplifier, 16 is a demodulator such as a synchronous detector, and 17 is a filter composed of an LPF. Now, assume that an external force is applied in the positive direction of the y-axis. At this time, since the inertial force is applied to the acceleration sensor in the negative y-axis direction, the mass body 4 is displaced in the negative y-axis direction. Since an electrode is formed on the mass body 4, the mass body 4 can be regarded as a movable electrode. Due to the displacement of the mass body 4, the capacitance of the capacitor formed by the mass body 4, the fixed electrode 6 and the fixed electrode 7 changes as compared to before the capacitor receives an inertial force. FIG. 2A shows this state, and FIG. 2B shows a state in which FIG. 2A is replaced with capacitors 10 and 11. An example of a detection circuit for detecting acceleration using the acceleration sensor element 14 is shown in FIG.
Examples of the detection circuit include a circuit for examining a change in oscillation frequency, a circuit for extracting a change in impedance due to a change in the capacitance of a capacitor, and a circuit for converting a differential amount of electrified charge into a voltage. Here, a description will be given of a configuration of a circuit that measures a change in impedance due to a change in capacitance of a capacitor due to displacement of the mass body 4 and calculates acceleration from the value.

FIG. 2C shows an example of the detection circuit.
The fixed electrode 6 is formed by the AC signal source 12 and the inverting amplifier 13,
A voltage whose phase is inverted is applied to the fixed electrode 7.
The sum of the inter-electrode distance between the fixed electrode 6 and the mass body 4 and the inter-electrode distance between the fixed electrode 7 and the mass body 4 is 2d, and the displacement of the mass body 4 from the equilibrium state (state in which no external force is applied) is Δd. Then, the differential capacitance ΔC and the current I flowing through the mass body 4 are expressed by the following equations. ΔC ≒ 2C0 × Δd / d (when Δd << d) (1) I = jω × ΔC × V (2) where C0: fixed electrode 6 or fixed electrode 7 in an equilibrium state The capacitance of a capacitor formed by the mass 4 and the current I: the current flowing through the mass 4 V: the voltage of the AC signal source 12 ω: the angular frequency of the AC signal source 12 t: time The current flowing through the mass 4 is charged by the charge amplifier 15 And converts this to a voltage. The signal is demodulated by a demodulator 16 including a synchronous detector at the subsequent stage. After this, LP
F due to displacement of the mass body 4 through a filter 17 such as F
It outputs a voltage signal proportional to the change in the differential capacitance of the two capacitors. An acceleration sensor according to the present invention, since such differential capacitance changes according to acceleration as has a configuration for detecting acceleration by the voltage signal output with the change in the differential capacitance. Furthermore, since the beam 3 and the mass body 4 have a shape having a rotational symmetry of 180 degrees in the wafer plane, the mass body 4 can be displaced in parallel to the inertial force in the y-axis direction. The displacement of the mass body 4 can be increased by displacing the mass body 4 in parallel, so that the change in the capacitance of the capacitor formed by the mass body 4 and the fixed electrodes 6 and 7 is increased. be able to.

FIG. 3 illustrates a method of manufacturing the acceleration sensor having the above-described configuration . In FIG. 3, 18 and 19 are oxide films, 20 is single crystal silicon, and the crystal plane is (11).
0) a device wafer having a surface, 21 an etching groove,
22 and 23 are passivation films made of an oxide film or a nitride film, 24 is a p-type or n-type impurity diffusion layer, 25 is a detection circuit IC for detecting acceleration, 26
Is a silicon IC substrate for incorporating the detection circuit IC 25, and 27 is a bonding wire. First, after an oxide film 18 having a thickness of about 3 μm is deposited on the device wafer 20, a pattern is formed on the oxide film 18 using a semiconductor lithography technique. Thereafter, an etching groove 21 having a depth of about 2 μm to 3 μm from the surface of oxide film 18 is formed by dry etching or wet etching. Further, since the etching groove 21 is for freely vibrating the completed mass body 4 and the beam 3, the substrate 9
An etching groove 21 may be provided on the upper oxide film 19. Thereafter, the device wafer 20 and the substrate 9 on which the oxide film 19 is deposited are fused and bonded (fusion bonding).
The two are joined using a technique (FIG. 3A).

Next, the surface of the device wafer 20 is polished to adjust the thickness of the device wafer 20 to a desired thickness (FIG. 3B). Thereafter, the passivation film 22 and the substrate 9 are protected to protect the surface of the device wafer 20.
Passivation film 23 to protect the surface of
It is formed on the surfaces of the device wafer 20 and the substrate 9 by the D method (LPCVD, PECVD, etc.) or the sputtering method. Thereafter, a plan view pattern of the structure constituting the acceleration sensor is formed on the surface of the passivation film 22 by dry etching (for example, reactive ion etching (RIE)).

However, when forming the pattern of the acceleration sensor on the surface of the passivation film 22, the device wafer 2
It is necessary to take into account the crystal plane orientation of 0. This is because when the etching process is performed on the device wafer 20, the progress of the vertical etching is faster than the progress of the horizontal etching, and after the etching process is completed,
If a vertical or nearly vertical cross-sectional shape is obtained, the gap between the electrode surfaces formed by the fixed electrode 6 and the mass body 4 formed by the device wafer 20, and the fixed electrode 7 and the mass body 4
This makes it possible to suppress the expansion of the gap between the electrode surfaces, and to form a structure in which the electrode surfaces formed by etching are both perpendicular to the surface of the device wafer 20.

The progress of the etching in the vertical direction is faster than the progress of the etching in the lateral direction, and after the etching process is completed, the etching is performed such that a cross-sectional shape perpendicular to the surface of the device wafer 20 is obtained. The method is called anisotropic etching. The crystal plane of the surface is (11
When the single crystal silicon (0) is etched, the crystal plane on the side surface formed by permeation of the etching solution is (11).
It is known that when etching is performed so that the (111) plane is perpendicular to the (0) plane, it is possible to considerably suppress the lateral progress of the etchant. Therefore, the device wafer 2 whose crystal surface is (110)
In order to perform anisotropic etching at 0, the (111) crystal plane on the side surface formed by the infiltration of the etchant is perpendicular to the (110) plane, which is the crystal plane of the surface of the device wafer 20. It is necessary to check the plane orientation of the crystal plane to be a plane.

As a method of examining the plane orientation of the crystal plane (111), the (111) plane is determined based on a major flat (orientation mark) attached to the device wafer 20 in order to confirm the crystal orientation of the device wafer 20. There is a way to find out. Alternatively, on the passivation film 22 of the device wafer 20 having a crystal plane of (110), several rectangular patterns for examining the plane orientation are formed by shifting the angles by, for example, 0.1 degrees in advance. Etching may be performed on the pattern to adopt a surface that minimizes the speed of the lateral etching (not shown).

As described above, the acceleration sensor is formed on the passivation film 22 of the device wafer 20 so that the crystal plane of the side surface formed by the anisotropic etching becomes the (111) plane perpendicular to the (110) plane. After forming the structure and the pattern of the fixed electrode, the anisotropic etching solution (for example, KOH, TMAH, hydrazine, C
Anisotropic etching is performed using sOH or the like until the pattern surface of the passivation film 22 reaches the boundary between the device wafer 20 and the oxide film 18. By this step, the vibrating body, which is a basic component of the acceleration sensor, and the fixed electrode 6
And a structure having the fixed electrode 7 are formed from the same device wafer 20 (FIG. 3C). The depth of the anisotropic etching depends on the gap between the electrodes of the acceleration sensor to be manufactured and the selectivity of the etching rate ((11
Ratio between the 0) plane etching rate and the silicon (111) plane etching rate), the structure of the acceleration sensor,
An appropriate value is selected depending on the required performance. In an acceleration sensor that detects acceleration from a change in capacitance, it is important to increase the inter-electrode capacitance by reducing the inter-electrode gap to increase the sensitivity. The gap between the formed electrodes depends on the patterning accuracy, the selectivity of the etching rate, and the etching depth. Therefore, assuming that the patterning accuracy and the selection ratio of the etching rate are constant values, the minimum value of the gap between the formed electrodes can be determined by the etching depth.
Therefore, even when anisotropic etching of a wafer having the same thickness is performed, anisotropic etching is performed from one direction and anisotropic etching is performed from both surfaces. Can be suppressed. Therefore,
In the step shown in FIG. 3A, after forming an etching groove 21 on the oxide film 18, a half of the thickness of the wafer is anisotropically formed using a nitride film having a pattern of a structure on the surface having the etching groove 21 as a mask. It may be preliminarily etched using a reactive etching (not shown).

Next, in the structure formed by etching from the device wafer 20, the passivation film 22 on the surface is removed by etching, and p-type or n-type impurities are diffused to the surface and side surfaces of the structure to form p-type impurities. Alternatively, an n-type impurity diffusion layer 24 is formed. By forming the impurity diffusion layer 24 on the surface and side surface of the structure, the conductivity of the fixed electrode 6, the fixed electrode 7, and the vibrator can be increased. However, the step of forming the impurity diffusion layer 24 may be omitted when the conductivity of the single crystal silicon as the material of the device wafer 20 is high. Thereafter, the oxide film 18 supporting the beam 3 and the mass body 4 of the vibrating body is removed by etching to release the beam 3 and the mass body 4 (FIG. 3).
(D)). Then, the metal electrode 8 is selectively metallized on the vibrating body of the structure formed from the device wafer 20, the fixed electrode 6 and the fixed electrode 7 by a sputtering device or the like (FIG. 3E).

Next, a silicon IC substrate 26 incorporating a separately prepared detection circuit IC25 in which a detection circuit for detecting acceleration is integrated is mounted on an acceleration sensor element formed by the above-described process using a die bonding agent. 14 on. Alternatively, it may be joined to the acceleration sensor element 14 by using a low-temperature fusion joining technique of silicon. Here, the detection circuit IC uses the low-temperature fusion bonding technology of silicon.
25 is to prevent thermal destruction (see FIG. 3).
(G)). After that, the structure and the metal electrode 8 on the detection circuit IC 25 are wired using the bonding wire 27. Then, they are separated into individual acceleration sensors by dicing. This dicing step is performed by the detection circuit IC25.
It may be performed before the silicon IC substrate 26 incorporating the semiconductor device and the acceleration sensor element 14 are joined.

Alternatively, instead of separately preparing a silicon IC substrate 26 on which a detection circuit IC25 in which a detection circuit for detecting acceleration is integrated as described above is mounted, the detection circuit IC25 is mounted on the device wafer 20 in advance. You may put it. Fig. 3
(B) After the process is completed, the detection circuit IC 25 may be formed on the device wafer 20 on a mirror-finished surface. Or
Detection circuit I integrated from device wafer 20 from the beginning
C25 may be incorporated. As described above, FIG.
Step (b), that is, after polishing the surface of the device wafer 20 and adjusting the thickness of the device wafer 20 to a desired thickness, the detecting circuit IC 25 is mounted on the mirrored surface on the device wafer 20 and passivation is performed. The film 22 is deposited, an acceleration sensor pattern is formed, and the vibrator, the fixed electrode 6, the fixed electrode 7, and the silicon IC substrate 26 are formed by anisotropic etching. Thereafter, the beam 3 and the mass body 4 are released by removing the passivation film 22 and removing the oxide film 18 exposed to the outside air by anisotropic etching. Then, the metal electrode 8
Is formed, and the metal electrodes 8 on the structure and the detection circuit IC 25 are wired using the bonding wires 27 (FIG. 3F). When such a method is used, the detection circuit IC2
The step of bonding the silicon IC substrate 26 incorporating the substrate 5 to the substrate 9 can be omitted.

The acceleration sensor can be manufactured by using the following method. This will be described with reference to FIG. That is, instead of depositing and patterning the oxide film 18 on the device wafer 20 and forming an etching groove 21 on the oxide film 18 by etching, the device wafer 2
The device wafer 20 by etching itself.
An etching groove 21 is formed in the device wafer 20. Thereafter, the oxide film 18 is formed on the device wafer 20 by thermal oxidation or sputtering.
(FIG. 4A). Then, it is bonded to the substrate 9 using silicon fusion bonding (FIG. 4B). Thereafter, the acceleration sensor can be manufactured also by taking steps after the step of FIG. By forming an etching groove 21 having an appropriate depth in the device wafer 20 by an etching technique and adjusting the depth (for example, several hundred μm) as shown in FIG.
The step (b), that is, the step of polishing the surface of the device wafer 20 and adjusting its thickness can be omitted.

Although the material of the substrate 9 is silicon, glass (for example, a material close to the linear expansion coefficient of silicon such as aluminosilicate or borosilicate glass) may be used.
Material may be used. An example of a process for manufacturing an acceleration sensor using the glass substrate 9 will be described with reference to FIG. In FIG. 5, reference numeral 28 denotes a passivation film made of an oxide film or a nitride film.

A passivation film 28 is deposited on the device wafer 20 in which the detection circuit IC 25 has been incorporated in advance, and an etching groove 21 is formed by etching (FIG. 5A). Next, after removing the passivation film 28, the device wafer 20 and the substrate 9 are bonded using anodic bonding (FIG. 5B). Alternatively, instead of directly anodically bonding the substrate 9 and the device wafer 20, the substrate 9 and the device wafer 20 may be anodically bonded via an insulating film such as an oxide film or a nitride film. Thereafter, a structure and a silicon IC substrate 26 are formed from the device wafer 20 by anisotropic etching (FIG. 5C). The passivation film 22 is removed, and the metal electrode 8 is selectively metallized on the structure (FIG. 5D). Alternatively, in order to perform anisotropic etching, a pattern of the metal electrode 8 is formed on the passivation film 22 before the pattern of the structure and the silicon IC substrate 26 is formed.
A metal electrode 8 made of u or the like may be formed.

Next, a plan view and a side view (FIGS. 6 and 7) of a state in which the acceleration sensor manufactured by any of the above-described methods is packaged are shown. 6 and 7, 29 is a lead pin, 30 is a stem, 31 is a cap, and 32 is an adhesive. The one shown is the detection circuit I
A package in which an acceleration sensor in which a silicon IC substrate 26 in which C25 is incorporated is bonded on the acceleration sensor element 14 is packaged (FIG. 6), and an acceleration sensor in which the detection circuit IC 25 is incorporated in a device wafer 20 is packaged (FIG. 7). ). When the detection circuit is not integrated, the components of the acceleration sensor except for the detection circuit IC25 on the ceramic substrate for the hybrid IC;
A detection circuit composed of discrete electronic components constituting the detection circuit may be mounted and packaged (not shown). When adjusting the frequency characteristics of the sensor, a pressure medium (for example, an inert gas such as air, nitrogen or Ar at a certain pressure) or a liquid (for example, silicon oil) is sealed in the cap 31 as necessary. do it.

In the step of packaging the acceleration sensor, fine dust and dust may enter between the electrodes of the acceleration sensor and adversely affect the acceleration sensor. Therefore, it is necessary to perform this step in a clean environment. There is. It is also necessary to protect the acceleration sensor from contamination by chips generated in the dicing process.

Further, a configuration as shown in FIG. 8 may be adopted. In FIG. 8, reference numeral 33 denotes an auxiliary support portion, reference numeral 34 denotes a protective substrate, and reference numeral 35 denotes an etching groove. Further, holes are formed in the protection substrate 34 at portions facing the etching grooves 35 and the metal electrodes 8. As shown in FIG.
Is formed so as to surround the side surface of the acceleration sensor element 14 (including the detection circuit IC 25 if the detection circuit IC 25 is formed on the same substrate), and the protection substrate 34 made of glass or the like is anodically bonded to the auxiliary support portion 33. The acceleration sensor is prevented from being contaminated. When performing anodic bonding, anodic bonding is performed using the auxiliary support portion 33 as an anode and the protective substrate 34 as a cathode. Alternatively, when the material of the substrate 9 is glass, anodic bonding may be performed using the substrate 9 as an anode and the protective substrate 34 as a cathode. Alternatively, anodic bonding may be performed using the substrate 9 and the auxiliary support portion 33 as anodes and the protective substrate 34 as cathodes. As the protective substrate 34, silicon having an insulating film such as an oxide film or a nitride film may be used. When the protection substrate 34 made of silicon having an insulating film is used, the low-temperature fusion bonding of silicon may be used for bonding with the auxiliary support portion 33. During anodic bonding, an inert gas may be introduced or the internal pressure may be adjusted to optimize the frequency characteristics of the acceleration sensor. In addition, by providing an electrode for electrically grounding the auxiliary support portion 33 and grounding it, stray capacitance can be stabilized and can be used as an electrostatic shield (not shown).

The structure of the acceleration sensor having the auxiliary support portion 33 and the protection substrate 34 thus formed is a detection circuit IC2.
5 and a detection circuit comprising discrete components are mounted on a substrate made of ceramics or the like, and can be housed in a simple plastic package (not shown). Thereby, the cost of the package of the acceleration sensor can be reduced, and a lower-cost acceleration sensor can be provided.

As shown in FIG. 8, an etching groove 35 is provided in advance in a portion of the protective substrate 34 in the vicinity of the vertically above the mass 4 by wet etching or the like, so that the mass 4 is excessively large in the vertical direction. It has the function of a stopper that prevents a large displacement. The etching groove 35 includes the mass 4 and the beam 3
Therefore, an etching groove 35 may be provided in the device wafer 20.

Reference Example 2 In the acceleration sensor of FIG. 9, reference numeral 36 denotes a damping adjustment mechanism for adjusting the frequency characteristics of the acceleration sensor.
When the mass body 4 is displaced by the inertial force, the side surfaces of all the mass bodies 4 perpendicular to the direction of displacement are subjected to a resistive force by a surrounding medium (a pressure medium or a liquid sealed to adjust the frequency characteristics). This resistance increases as the area of the side surface perpendicular to the vibration direction of the mass body 4 increases. In the acceleration sensor of FIG. 1, since the fixed electrode 6 and the fixed electrode 7 are arranged so as to face the mass body 4, it can be said that these components themselves have a damping adjustment function. But,
The desired resistance may not be obtained only by the area of the side surface of the acceleration sensor shown in FIG. 1 that is perpendicular to the vibration direction of the mass body 4.

In the acceleration sensor shown in FIG. 9, in order to increase the area of the side surface perpendicular to the vibration direction of the mass body 4, two opposing sides of the mass body 4 are formed in a comb shape, and the comb shape is opposed to the comb shape. Is provided with the damping adjustment mechanism 36 of FIG. As a result, a new (111) crystal plane is formed at an angle of 35.26 degrees with respect to the crystal plane (110) of the surface of the structure. This is formed by performing anisotropic etching on a portion where the angle between two (111) planes perpendicular to the (110) plane, which is the crystal plane of the surface of the structure, is 70.53 degrees. . In Reference Example 1 , the design is made so that the (111) plane that forms an angle of 35.26 degrees with the (110) plane does not occur. When the (111) plane which forms an angle of 35.26 degrees with the (110) plane is formed by performing anisotropic etching, it must be designed such that this plane does not hinder the movement of the mass body 4.

The resistive force received when the mass body 4 of the acceleration sensor is displaced by inertial force is proportional to the area of the side surface of the mass body 4 perpendicular to the vibration direction. Therefore, by adjusting the comb-shaped damping adjusting mechanism 36 and the number and length of the combs of the mass body 4, it is possible to adjust the resistance force received by the mass body 4. It is possible to arbitrarily adjust the frequency characteristic (for example, critical attenuation state: ζ = 0.707, ζ: attenuation coefficient). This frequency characteristic can also be adjusted by changing the gas pressure in the package or by filling a viscous liquid.

By designing the gap of at least one pair of the comb-shaped pair formed by the comb-shaped damping adjusting mechanism 36 and the mass body 4 to a certain value,
It is also possible to provide a stopper function for preventing the beam 3 from breaking due to the large displacement of the mass body 4 due to excessive impact acceleration, or preventing the mass body 4 and the fixed electrode from being attracted by electrostatic attraction. As described above, by providing the damping adjusting mechanism 36 having the comb-shaped structure and the mass body 4, the frequency characteristics,
It is possible to provide an acceleration sensor excellent in impact resistance and reliability.

Reference Example 3 FIG. 11 shows an example of the acceleration sensor of Reference Example 3. FIG.
In the figures, 38 and 39 are comb-shaped fixed electrodes, and 40 is an actuating electrode. The comb of the mass 4 is
And the gap between the adjacent comb of the fixed electrode 39 and the comb of the adjacent fixed electrode 39 are arranged asymmetrically such that one is smaller than the other. This is because, when the mass body 4 is displaced by the inertial force, the capacitor formed in a portion where the gap between the comb of the mass body 4 and the adjacent fixed electrode 39 is small is smaller than the capacitor of the fixed electrode 39 adjacent to the comb of the mass body 4. This is because the value of the gap is designed so that the capacitance can be changed sufficiently larger than that of a capacitor formed in a portion having a large gap with the comb. Thus, the gap between the comb of the mass body 4 and the comb of the adjacent fixed electrode 39 forms a comb-shaped electrode pair 37 in a portion where one is smaller than the other, and the capacitor is formed by one comb-shaped electrode pair. Has formed. The same relationship exists between the comb of the mass body 4 and the comb of the adjacent fixed electrode 38.
Further, the comb-shaped electrode pair 3 formed by the mass body 4 and the fixed electrode 38
7 is equal to the gap between the mass body 4 and the fixed electrode 6, and the gap between the comb-shaped electrode pair 37 formed by the mass body 4 and the fixed electrode 39 is set between the mass body 4 and the fixed electrode 7. Is equal to the gap. Further, the fixed electrode 6 and the fixed electrode 38 are electrically connected externally, and the fixed electrode 7 and the fixed electrode 39 are electrically connected externally. Alternatively, the fixed electrode 6 and the fixed electrode 38 may be made common from the beginning, and the fixed electrode 7 and the fixed electrode 39 may be made common.

When the acceleration is detected from the change in the capacitance of the capacitor, the acceleration can be detected with higher sensitivity as the capacitance of the capacitor formed by the mass body 4 and the fixed electrode is larger. The capacitance of the capacitor is proportional to the electrode area. Therefore, the fixed electrode 38 and the fixed electrode 3
9, the mass body 4 is comb-shaped, and the gap between the comb-shaped electrode pair 37 formed by the mass body 4 and the fixed electrode 38 is set to be equal to the gap between the mass body 4 and the fixed electrode 6; Comb-shaped electrode pair 3 formed by 4 and fixed electrode 39
7 is set to be equal to the gap between the mass body 4 and the fixed electrode 7 and the number of comb-shaped electrode pairs 37 is increased so that the capacitance of the capacitor is limited within a limited area (even if the element size is the same). It is possible to increase the capacitance. By composing the fixed electrode 38 and the fixed electrode 39 with a comb-shaped electrode, the fixed electrode 38 and the fixed electrode 39 are formed.
Has a function of adjusting the damping and a function of increasing the capacitance of the capacitor. Therefore, in designing the number of pairs of the comb-shaped electrode pairs 37, it is necessary to take the both into consideration.

In FIG. 11, a cavity is provided in the mass body 4,
An actuating electrode 40 is provided therein. This allows the acceleration sensor to have a self-diagnosis function. That is, when a potential difference is generated between the actuating electrode 40 and the mass body 4, the mass body is displaced by electrostatic attraction. This electrostatic attraction is apparently the same as when an external force is applied to the acceleration sensor, and it can be diagnosed from the value output with the change in the capacitance of the capacitor whether or not the mass body 4 of the acceleration sensor is reliably displaced by this. .
In this sense, the acceleration electrode 40 is provided in the acceleration sensor.
It is possible to provide a self-diagnosis function by providing the function. Alternatively, a part of the fixed electrode 38 can be electrically disconnected to form an actuating electrode. The actuating electrode 40 can be applied to FIGS. 1, 8, and 9 and FIGS. 12, 13, and 16 described later. Further, a stopper that limits displacement of the mass body 4 by disposing any pair of the fixed electrode 6 and the fixed electrode 38 or the pair of the fixed electrode 7 and the fixed electrode 39 slightly closer to the mass body 4 with respect to the other pair. It is also possible.

Reference Example 4 FIG. 12 shows an example of the acceleration sensor of Reference Example 4. FIG.
Is a mass projecting portion. By making the beam 3 not protrude from the mass body 4 as shown in FIG. 12 but along one side of the mass body 4, the acceleration sensor can be manufactured more compactly. The vibrating body has a mass projecting portion 4.
By providing 1, the self-stopper can be achieved by designing the distance between the beam 3 and the anchor 5 and the mass projecting portion 41 to be smaller than the distance between the beam 3 and the fixed electrode.

FIG. 13 is an improvement of FIG. In FIG. 13, reference numeral 42 denotes a mass body mass adjustment hole for adjusting the mass of the mass body 4. FIG. 13 shows a comb-shaped fixed electrode 6 and a fixed electrode 7 and a damping adjustment mechanism 3.
6, an actuating electrode 40, and a mass body mass adjusting hole 42. The mass of the mass body 4 can be adjusted by the size of the mass body mass adjustment hole 42. Thus, the frequency characteristics and the sensitivity of the acceleration sensor can be adjusted by changing the size of the mass adjusting hole 42 without changing the length of the beam 3.

Reference Example 5 FIG. 14 shows a structure in which the beam 3 and the anchor 5 are formed inside the mass body 4. In the case where the structure has two anchors as in the previous reference examples , when the material of the substrate 9 is different from that of the structure, the coefficient of linear expansion is different, and thus the substrate 9 is changed by temperature change.
In addition, there is a problem that a stress is generated in the beam 3 due to strain generated in the two anchors 4 of the vibrating body. When the vibrating body has such a structure, even if the substrate 9 has a different linear expansion coefficient,
The beam 3 is not stressed by the strain generated in the anchor.

Reference Example 6 FIG. 15 shows two acceleration sensors whose displaceable directions are orthogonal to each other manufactured on the same substrate. In FIG. 15, reference numeral 43 denotes an x-axis direction acceleration sensor for detecting acceleration in the x-axis direction, and reference numeral 44 denotes a y-axis direction acceleration sensor for detecting acceleration in the y-axis direction. This makes it possible to measure accelerations in two axes, x-axis and y-axis.

Embodiment 1 Embodiment 1 is an angular velocity sensor capable of detecting an angular velocity of an object the rotational movement, angular velocity according to the present invention
9 shows a degree sensor . FIG. 16 is a plan view (a) showing a configuration of an angular velocity sensor for detecting an angular velocity of a rotating object, and a sectional view (b) of FIG. FIG.
In the figure, 45 is a drive electrode, 46 and 47 are vibration monitoring electrodes, and 48 and 49 are lower fixed electrodes. The vibrating body of this angular velocity sensor includes four beams 3, two masses 4, and three anchors 5. The structure of the angular velocity sensor is composed of a vibrating body and a driving electrode 4.
5, a vibration monitoring fixed electrode 46 and a vibration monitoring electrode 47 are provided. The specific structure of this sensor is such that a driving electrode 45 as a fixed electrode is arranged between two masses 4 having the same electric potential in the vibrating body, and a vibration monitoring fixed electrode is provided outside each mass 4. 46 and a fixed electrode 47 for vibration monitoring. In this angular velocity sensor, a structure having a vibrating body, a drive electrode 45, a vibration monitoring fixed electrode 46, and a vibration monitoring fixed electrode 47 is formed from the same wafer by anisotropic etching. Further, a lower fixed electrode 48 for detecting vibration of the mass body 4 and a lower fixed electrode 49 are provided on the substrate 9 located on the lower surface of each mass body 4. Further, by providing an electrode for electrically grounding the auxiliary support portion 33 and grounding the same as the acceleration sensor, the stray capacitance can be stabilized and can be used as an electrostatic shield (not shown). ).

Next, the operation of the angular velocity sensor will be described with reference to FIG. In FIG. 17, reference numerals 50 and 51 denote capacitors constituted by the mass body 4 and lower fixed electrodes 48 and 49; 52, a DC bias voltage source;
(Auto gain control) circuit, 54 is a CV (capacitance-voltage) converter, and 58 is an AC voltage source. AC voltage source 58 connected to drive electrode 45 and D for bias
With the C bias voltage source 52, the two mass bodies 4 are excited and oscillated according to the frequency of the AC voltage source 58 with a phase difference of 180 degrees due to an electrostatic attraction generated between the two mass bodies 4 and the drive electrode 45. At this time, when there is an angular velocity vector Ωx in the horizontal axis direction shown in the plan view of FIG.
In the case where there is an angular velocity Ωx caused by the rotational movement about the horizontal axis, Coriolis force as inertia force is generated in the mass body 4 in the direction shown in FIG.
Therefore, when rotating, the mass 4 of this sensor is used.
Vibrates in such a manner that the vibration excited by the AC voltage source 58 and the vibration caused by the Coriolis force generated by the rotational motion are superimposed.
The direction of the excitation vibration caused by the electrostatic attraction generated by the AC voltage source 58 and the direction of the vibration caused by the Coriolis force generated by the rotational motion are orthogonal to each other.

The displacement u in the y direction due to the excitation vibration of the mass body 4
It is assumed that the speed uy ′ in the y and y directions has the following relationship. uy = A × sin (ωrT) (3) uy ′ = A × ωr × cos (ωrT) (4) A: y of the mass body 4 Maximum displacement in direction ωr: angular frequency of y-direction vibration of mass body 4 When rotating, the mass body 4 generates a Coriolis force Fc proportional to uy ′, the direction of which is as shown in FIG. The Coriolis force Fc is expressed as follows:
Assuming that the mass of each mass body 4 is m, there is the following relationship: Fc = 2Ωx × mxuy ′ (5) Further, the relationship between the Coriolis force Fc and the displacement uz in the z direction is as follows, where the rigidity in the z direction is kz: Fc = kz × uz (6) From these two equations (6) and (7), uz = (2Ωx × mxuy ′) / kz (7) From this, it can be seen that the change in the capacitance between the mass body 4 and the lower fixed electrode 48 and the change in the capacitance between the mass body 4 and the lower fixed electrode 49 change in a form modulated by the excitation vibration. . FIG. 17A shows this state, and FIG. 17B shows this equivalent circuit. FIG. 17C shows an example of a detection circuit configuration for detecting the angular velocity.

The excitation vibration displacement u in the y direction of the two mass bodies 4
Since y is 180 degrees out of phase with each other, the phases of the Coriolis forces Fc acting on the two mass bodies are also 180 degrees out of phase with each other. Therefore, the capacitance of the capacitor formed by the mass body 4 and the lower fixed electrode 48, and the mass body 4 and the lower fixed electrode 49
The capacitance of the capacitor formed by one increases when the other increases and the other decreases. The voltage proportional to the change in the differential capacitance is shown in FIG.
The circuit is taken out as shown in FIG. This detection circuit is shown in FIG.
The basic configuration is the same as (c). The difference is that a DC bias voltage source 52, an AC voltage source 58, an AGC (auto gain control) circuit 53, a vibration monitor electrode 46, and a vibration monitor electrode 47 are provided to excite and vibrate the mass body at a constant amplitude. is there. Further, the CV (capacitance-voltage) converter 54 is provided with the components 12, 13, 1 in FIG.
It is represented by a circuit formed by 5, 16, and 17.

Next, an example of a manufacturing process of an angular velocity sensor for detecting the angular velocity of the rotating object will be described with reference to FIG. FIG. 18 is a view showing a manufacturing process of the angular velocity sensor when the material of the substrate 9 is glass (for example, a material close to the linear expansion coefficient of silicon such as aluminosilicate or borosilicate glass). The manufacturing process of this sensor is
There are many points in common with the manufacturing process of an acceleration sensor for detecting the acceleration of a linearly moving object. Here, the beam 3 needs to have the same width and thickness. This is because the driving frequency of the vibration in the y-axis direction uses the structural resonance point in the vibration direction or its vicinity in order to increase the detection sensitivity. This is because it is desirable to keep them common.

First, an etching groove 21 is formed on a device wafer 20 by photolithography and etching, and then an oxide film 1 is formed on the surface where the etching groove 21 is formed.
8 is formed. In this case, the sensitivity of the angular velocity detection depends on the capacitance of the capacitor formed by the mass body 4 and the lower fixed electrodes 48 and 49. The etching groove 21 defines an amount by which the mass body 4 can be displaced. That is, the detection sensitivity is the etching groove 2
Since it depends on the depth of 1, the thickness is about several μm (for example, 2 μm to 3 μm). On the other hand, the lower fixed electrode 48
Then, the lower fixed electrode 49 is selectively metallized by vapor deposition or sputtering (FIG. 18A). Alternatively, the metal electrode 8 may be formed by lift-off. After this,
The device wafer 20 and the substrate 9 are aligned, and anodic bonding is performed. Next, the thickness of the device wafer 20 is adjusted. The drive frequency of the vibration in the y-axis direction is common to the resonance point in the z-axis direction which is modulated by this frequency in order to utilize the resonance point in or near the structure in the vibration direction in order to increase the detection sensitivity. It is desirable to keep. Therefore, the thickness of the device wafer 20 may be adjusted to be the same as the width of the beam 3 formed from the device wafer 20 (FIG. 18B). Alternatively, it is also possible to adjust the frequency characteristics and sensitivity of the angular velocity sensor by providing a mass body mass adjustment hole 42 (not shown) in the mass body 4 for adjusting the mass of the mass body 4.

When the substrate 9 is made of silicon, it is necessary to insulate the substrate 9 from the lower fixed electrode 48 and the lower fixed electrode 49. Therefore, an insulating film made of an oxide film or a nitride film is formed on the surface of the substrate 9. After the pattern of the lower fixed electrode 48 and the lower fixed electrode 49 is formed, the lower fixed electrode 48 and the lower fixed electrode 49 are selectively metallized by vapor deposition or sputtering. Or lower fixed electrode 4
After forming the resist pattern of the lower fixed electrode 8 and the lower fixed electrode 49, the lower fixed electrode 48 and the lower fixed electrode 49 may be formed by vapor deposition or sputtering and lift-off.
Alternatively, impurity diffusion layers formed by diffusing p-type or n-type impurities into the substrate 9 itself using an insulating film made of an oxide film or a nitride film as a mask may be used as the lower fixed electrodes 48 and 49 (not shown). Zu). Thereafter, the device wafer 20 and the substrate 9 are aligned, and both are joined by low-temperature fusion joining.

Next, PEC is applied to the surface of the device wafer 20.
After depositing a passivation film 22 made of a nitride film or an oxide film by VD or sputtering or the like, patterning is performed (FIG. 18C). In this case, when anisotropic etching is used when etching the device wafer 20 in the next step, the etching must be performed in consideration of the crystal direction of the device wafer 20. How to find the crystal direction,
Since the anisotropic etching has already been described,
Here, it is omitted.

Next, the vibrating body is formed by anisotropically etching the device wafer 20 using wet etching with an anisotropic etching solution or dry etching (for example, reactive ion etching (RIE)).
A structure having a driving electrode 45, a vibration monitoring fixed electrode 46, and a vibration monitoring fixed electrode 47, and an auxiliary support portion 54 are formed, the passivation film 22 is removed, and the metal electrode 8 is selected by vapor deposition or sputtering. Metallize (FIG. 18D). Alternatively, the structure and the silicon I are formed on the passivation film 22 to perform anisotropic etching.
The pattern of the metal electrode 8 may be formed before the pattern of the C substrate 26 is formed, and the metal electrode 8 made of Cr, Au, or the like may be formed by lift-off.

Next, in a reduced pressure atmosphere (for example, in a vacuum or a state close to a vacuum), a protection substrate 34 (in this example, the material is glass) having a hole at a portion facing the etching groove 35 and the metal electrode 8, and a device wafer And 20 are anodically bonded. When performing anodic bonding, anodic bonding is performed using the auxiliary support portion 33 as an anode and the protective substrate 34 as a cathode. Or, the substrate 9
When the material is glass, anodic bonding may be performed using the substrate 9 as an anode and the protective substrate 34 as a cathode. Alternatively, anodic bonding may be performed using the substrate 9 and the auxiliary support portion 33 as anodes and the protective substrate 34 as cathodes. Protection substrate 3
When 4 is silicon, low temperature fusion bonding is performed. In an angular velocity sensor that detects the angular velocity of a rotating object,
In order to utilize the resonance phenomenon of the mass body, it is necessary to minimize damping (for example, damping due to air viscosity or squeeze damping) generated between the mass body and other electrodes. Therefore, the etching groove 35 of the protection substrate 34
The cavity around the mass body 4 formed by the etching grooves 21 of the device wafer 20 is desirably in a vacuum or in a state close to a vacuum (FIG. 18E).

Through the above steps, the structure of the angular velocity sensor for detecting the angular velocity of the rotating object is completed. This step has many parts in common with the aforementioned manufacturing process of the acceleration sensor for detecting the acceleration of the linearly-moving object, and therefore, the manufacturing process of the acceleration sensor for detecting the acceleration of the linearly-moving object is used. It is possible to manufacture an angular velocity sensor for detecting an angular velocity. Further, a detection circuit IC 25 for detecting the angular velocity can be formed on the substrate 9.

In two angular velocity sensors for detecting the angular velocity of a rotating object, two vibration axes having different rotation directions are arranged on the same substrate so that the vibration excitation directions by the AC voltage source 58 are orthogonal to each other. On the other hand, an angular velocity sensor capable of detecting the angular velocity is provided (not shown).

The angular velocity sensor according to the first embodiment and the reference
Angular velocity sensor capable of detecting the acceleration due to angular velocity and the linear motion by the rotary motion by at least one of the pressurized <br/> speed sensor as described in Reference Example 5 from Example 1 fabricated on the same substrate it can. (Not shown)

[0058]

The angular velocity sensor according to the first configuration of the present invention.
Sa includes a substrate, and bonded to the substrate, and a wafer made of monocrystalline silicon and a made structure by etching, the structure is located a gap with respect to the substrate 2 One of the mass body, and supporting a respective said mass body, and a beam positioned with a gap with respect to the substrate, the vibrating body having a anchor supports the beams, and is bonded to the substrate, the For vibration monitor located outside each mass
A fixed electrode, a fixed electrode located between the masses, and a lower fixed electrode located on the lower surface of each mass,
An angular velocity sensor , wherein each of the mass bodies is a movable electrode, and the displacement of the movable electrode is electrically detected.
An auxiliary supporting portion around the structure, and a protective substrate for sealing said structure over said auxiliary supporting unit, the protective substrate, while the structure is closed, each quality A groove in which the mass body and the beam can freely vibrate, and a hole provided only in a portion facing the metal electrode provided in each of the anchor and each of the fixed electrodes, and a cavity around the mass body is provided. Since the reduced pressure atmosphere is used, a highly reliable angular velocity sensor can be obtained, and the cost of the package can be reduced.

In the angular velocity sensor according to the second configuration of the present invention, in the first configuration, the auxiliary support portion is separated from the structure, and the auxiliary support portion is provided with an electrode, Since the section is grounded, there is an effect that stray capacitance can be stabilized.

The method of manufacturing an angular velocity sensor according to the present invention includes the following steps (1) to (4), and it is possible to provide an angular velocity sensor with high sensitivity and high reliability. Ma
Also, the damping that occurs between the mass and other electrodes
There is an effect that can be suppressed. (1) A substrate on which two lower fixed electrodes are formed and a wafer made of single-crystal silicon having a surface with a (110) crystal plane and two etching grooves are fixed to the etching grooves and the lower part. process and the electrode are joined to face, (2) is deposited back on the insulating film on the side having the etch groove of the wafer, unnecessary insulating using an etching to obtain the desired pattern on the insulating film After removing the film, the (111) of the wafer is anisotropically etched.
By etching along a plane, two mass body located with a gap with respect to the substrate, it the mass body
Supports, respectively, and a beam positioned with a gap with respect to the substrate, to support the the beams, and the vibrating body and a anchor joined to the substrate, located on the outside of the respective mass Shake
Dynamic monitor fixed electrode, the fixed electrode located between said respective mass, and step (3) to form the auxiliary support section located around the structure composed of said vibrating body and the respective fixed electrodes and the anchor A step of selectively metallizing a metal electrode on each of the fixed electrodes (4) a groove in which each of the mass bodies and the beam can vibrate, and a portion facing the metal electrode provided on each of the anchor and each of the fixed electrodes; A protective board with holes only
Placed on the wafer, the protection substrate and the wafer
Anodic bonding process under reduced pressure atmosphere

[Brief description of the drawings]

FIG. 1 is a plan view and a cross-sectional view of an acceleration sensor according to a reference example 1 of the present invention.

FIG. 2 is a diagram illustrating a detection principle of an acceleration sensor according to a first embodiment of the present invention , a diagram illustrating an equivalent circuit thereof, and a diagram illustrating an example of a detection circuit for detecting acceleration.

FIG. 3 is a diagram illustrating an example of a manufacturing process of the acceleration sensor of Reference Example 1 according to the present invention.

FIG. 4 is a diagram illustrating an example of a manufacturing process of the acceleration sensor of Reference Example 1 according to the present invention.

FIG. 5 is a diagram illustrating an example of a manufacturing process of the acceleration sensor of Reference Example 1 according to the present invention.

FIG. 6 is a diagram illustrating an example of the packaging of the acceleration sensor according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of the packaging of the acceleration sensor according to the first embodiment of the present invention.

FIGS. 8A and 8B are a plan view and a cross-sectional view, respectively, when the acceleration sensor of Reference Example 1 according to the present invention is packaged on a glass substrate.

FIG. 9 is a plan view and a sectional view of an acceleration sensor according to a reference example 2 according to the present invention.

FIG. 10 is a diagram showing a change in gain with respect to a frequency when damping adjustment is performed and not performed on the acceleration sensor of Reference Example 2 according to the present invention.

FIG. 11 is a plan view and a sectional view of an acceleration sensor according to a third embodiment of the present invention.

FIG. 12 is a diagram illustrating an example of an acceleration sensor according to a fourth embodiment of the present invention.

FIG. 13 is a diagram illustrating an example of an acceleration sensor according to a fourth embodiment of the present invention.

FIGS. 14A and 14B are a plan view and a cross-sectional view illustrating an example of an acceleration sensor of Reference Example 5 according to the present invention.

FIG. 15 is a diagram illustrating an example of an acceleration sensor according to a sixth embodiment of the invention.

FIG. 16 is a plan view and a sectional view of the angular velocity sensor according to the first embodiment of the present invention.

FIG. 17 is a diagram illustrating a detection principle of the angular velocity sensor according to the first embodiment of the present invention, a diagram (b) illustrating an equivalent circuit thereof, and a diagram illustrating an example of a detection circuit for detecting the angular speed.

FIG. 18 is a diagram illustrating an example of a manufacturing process of the angular velocity sensor according to the first embodiment of the present invention.

FIG. 19 is a diagram showing a conventional acceleration sensor.

[Explanation of symbols]

3: Beam 4: Mass body 5:
Anchor 6: Fixed electrode 7: Fixed electrode 8:
Metal electrode 9: Substrate 10: Capacitor 1
1: Capacitor 12: AC signal source 13: Inverting amplifier 1
4: acceleration sensor element 15: charge amplifier 16: demodulator 1
7: Filter 18: Oxide film 19: Oxide film 2
0: Device wafer 21: Etching groove 22: Passivation film 23: Passivation film 2
4: impurity diffusion layer 25: detection circuit IC 26: silicon IC substrate 2
7: bonding wire 28: passivation film 2
9: Lead pin 30: Stem 31: Cap 3
2: adhesive 33: auxiliary support part 34: protective substrate 3
5: Etching groove 36: Damping adjustment mechanism 37
Comb electrode pair 38: Fixed electrode 39: Fixed electrode 4
0: Actuating electrode 41: Mass projecting part 4
2: Mass body mass adjustment hall 43: x-axis direction acceleration sensor 4
4: Y-axis direction acceleration sensor 45: Drive electrode 46: Vibration monitor electrode 4
7: Vibration monitoring electrode 48: Lower fixed electrode 49: Lower fixed electrode 5
0: Capacitor 51: Capacitor 52: DC bias voltage source 53: AGC (auto gain control) circuit 54: CV (capacitance-voltage) converter 5
5: Silicon substrate 56: Glass substrate 57: Glass substrate 5
8: AC voltage source

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-123628 (JP, A) JP-A-62-14978 (JP, A) JP-A-5-340959 (JP, A) 163934 (JP, A) JP-A-8-32090 (JP, A) JP-A-57-169645 (JP, A) JP-A-58-731 (JP, A) JP-A-5-503994 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 29/84 G01P 15/125

Claims (3)

(57) [Claims] 1. A semiconductor device comprising: a substrate; and a structure bonded to the substrate and formed by etching a wafer made of single crystal silicon, wherein the structure has a gap with respect to the substrate. Two masses, a beam that supports each of the masses, and is positioned with a gap to the substrate, and an anchor that supports the beam and joins the substrate. vibrator having a vibration mode which is located outside of the respective mass
The fixed electrode for the brush and the fixed electrode
Poles, and the comprises a lower fixed electrode located on the lower surface of each mass, <br/> the respective mass and the movable electrode, the angular velocity sensor characterized by electrically detecting the displacement of the movable electrode In addition, an auxiliary support portion around the structure, and a protective substrate for sealing the structure on the auxiliary support portion, the protection substrate, the structure, while the structure is sealed, A groove in which each of the mass bodies and the beam can freely vibrate, and a hole provided only in a portion facing the metal electrode provided in each of the anchor and each of the fixed electrodes, and a cavity around the mass body is subjected to a reduced pressure atmosphere. Angular velocity sensor
Sa. 2. The angular velocity sensor according to claim 1, wherein the auxiliary support is separated from the structure, an electrode is provided on the auxiliary support, and the auxiliary support is grounded.
Sa. 3. A method for manufacturing an angular velocity sensor , comprising the following steps (1) to (4). (1) A substrate on which two lower fixed electrodes are formed and a wafer made of single-crystal silicon having a surface with a (110) crystal plane and two etching grooves are fixed to the etching grooves and the lower part. process and the electrode are joined to face, (2) is deposited back on the insulating film on the side having the etch groove of the wafer, unnecessary insulating using an etching to obtain the desired pattern on the insulating film After removing the film, the (111) of the wafer is anisotropically etched.
By etching along a plane, two mass body located with a gap with respect to the substrate, it the mass body
Supports, respectively, and a beam positioned with a gap with respect to the substrate, to support the the beams, and the vibrating body and a anchor joined to the substrate, located on the outside of the respective mass Shake
Dynamic monitor fixed electrode, the fixed electrode located between said respective mass, and step (3) to form the auxiliary support section located around the structure composed of said vibrating body and the respective fixed electrodes and the anchor A step of selectively metallizing a metal electrode on each of the fixed electrodes (4) a groove in which each of the mass bodies and the beam can vibrate, and a portion facing the metal electrode provided on each of the anchor and each of the fixed electrodes; A protective board with holes only
Placed on the wafer, the protection substrate and the wafer
Anodic bonding process under reduced pressure atmosphere