JPH11183517A - Dynamical quantity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stop the influence of the rotation of a movable part in a plane parallel to the top surface of a base substrate on sensor sensitivity. SOLUTION: A weight movable electrode 16 supported on an anchor part 13 on the base substrate through spiral beam parts 14 and 15 having parts where plane shapes overlap with each other can be displaced almost in prallel to the top surface of the base substrate and its outer peripheral surface is a detection surface 16a. A fixed electrode has a detected surface 17a in such a shape that the weight movable electrode 16 is surrounded. While acceleration exceeding a specific level is applied, the detection surface 16a and detected surface come into contact with each other as the weight movable electrode 16 is displaced and a detecting circuit detects their contact. A through hole 19 is bored in the weight movable electrode 16, the base substrate is provided with a stopper shaft 20 entering the through hole 19, and the rotation of the movable electrode 16 is restricted by the through hole 19 and stopper shaft 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic quantity sensor for detecting a dynamic quantity such as acceleration based on a displacement of a movable section supported by a beam with respect to an anchor section.

[0002]

2. Description of the Related Art For example, it is built in a gas flow meter and is used to close a valve of a gas pipe when vibration such as an earthquake is detected, or when it is built in a combustion stove and detects vibration such as an earthquake. 2. Description of the Related Art Acceleration sensors used for cutting off flames and fuel are generally configured to detect accelerations in multiple directions in a two-dimensional plane with almost the same sensitivity. In such an acceleration sensor, it is required to realize improvement in reliability and productivity as well as downsizing and low power consumption. As disclosed in JP-A-9-145740, a semiconductor acceleration sensor manufactured using a surface micromachining technique is known.

That is, FIGS. 19 and 20 show a cross-sectional structure and a schematic vertical cross-sectional structure of a semiconductor acceleration sensor described in this publication. These FIGS. 19 and 20
In the above, on the support substrate 1 made of single crystal silicon,
The anchor part 3 is fixed via the support anchor 2a. The pair of beams 4 and 5 have one ends integrally connected to both sides of the anchor portion 3 and are provided so as to be elastically deformable in a direction parallel to the surface of the support substrate 1, and their planar shapes overlap each other. It is formed in a spiral shape having a portion. An annular weight movable electrode 6 (hereinafter also referred to as a movable portion) is integrally connected to the free ends of the beams 4 and 5 so as to be concentrically arranged with the anchor 3.
The weight movable electrode 6 has a configuration in which an outer peripheral surface, that is, a cylindrical side surface in a direction perpendicular to the support substrate 1 functions as a detection surface 6a having conductivity.

[0004] On the support substrate 1, a fixed electrode 7 is arranged via a support anchor 2b. The fixed electrode 7 is provided so as to surround the weight movable electrode 6. The cylindrical inner peripheral surface facing the weight movable electrode 6 functions as a conductive detection surface 7 a. ing. In this case, the anchor part 3, the beam parts 4 and 5, the weight movable electrode 6, and the fixed electrode 7 are formed by etching a silicon single crystal substrate bonded on the support substrate 1 via a silicon oxide film. The silicon oxide film is provided as a thin film for a sacrificial layer, and the support anchors 2a and 2b are formed by selectively etching a part of the silicon oxide film with a hydrofluoric acid-based etchant. Is what is done.

[0005]

In the above-mentioned conventional structure, since the beams 4 and 5 are formed in a spiral shape overlapping each other, when the liquid penetrates between them and a surface tension acts. The surface tension acts as a force for rotating the weight movable electrode 6 about the anchor portion 3. This may occur during a manufacturing process such as when etching a sacrificial layer thin film (silicon oxide film), and may also occur when the sensor is actually used. Therefore, in some cases, as shown in FIG. 21, the adjacent beam portions 4 and 5 may adhere to each other, and the attached state may be maintained as it is even after the etching solution is dried. In such a state, the detection sensitivity may be significantly reduced, or in some cases, the function as the acceleration sensor may be lost. Further, even when the weight is not attached, the rotation of the weight movable electrode 6 changes the spring constants of the beams 4 and 5, which may affect the detection sensitivity.

The present invention has been made in view of the above circumstances, and provides an acceleration sensor having a movable portion that can be displaced in an arbitrary axis direction substantially parallel to the surface of a support substrate. It is an object of the present invention to suppress the influence on the sensor sensitivity due to the rotation of the movable part.

[0007]

According to the first aspect of the present invention, the movable portion supported on the supporting substrate by the beam portion comprises:
When a mechanical quantity acts from the outside, it is displaced in an arbitrary axis direction substantially parallel to the support substrate surface, and based on such a displacement, the mechanical quantity acting on the movable portion can be detected. In this case, the support substrate is provided with rotation limiting means for limiting the rotational movement of the movable portion in a plane parallel to the surface of the support substrate. Therefore, during the manufacturing process or during actual use, the support substrate is provided. The rotation of the operating part in a plane parallel to the surface of the first member is prevented by the rotation restricting means. For this reason, it is possible to reliably suppress the influence on the sensor sensitivity due to the rotation of the movable part for detecting the physical quantity.

According to the second aspect of the present invention, the rotation restricting means is formed so as to be located at a portion where the movable portion is partially removed, so that the sensor is provided while the rotation restricting means is provided. There is no danger that the area efficiency will be degraded.

According to the third aspect of the present invention, the beam portion for supporting the movable portion is formed in a spiral shape having a planar shape having an overlap portion, and is elastically deformable in a direction parallel to the surface of the support substrate. The movable part comes to be sensitively displaced when a mechanical quantity acts,
Further, since the movable portion is formed in an annular shape, the inside of the movable portion can be effectively used, and the area efficiency as a sensor is improved.

According to the fourth aspect of the present invention, since the movable portion and the rotation restricting means are formed of the same material, they can be easily manufactured.

According to the fifth aspect of the present invention, the weight movable electrode supported by the anchor portion via the beam portion is provided when a dynamic quantity including a component parallel to the surface of the support substrate is applied from the outside. Then, the displacement occurs in a direction parallel to the surface of the supporting substrate, and the distance between the detection surface of the movable electrode and the detection surface of the fixed electrode changes accordingly. The detecting means detects the applied dynamic quantity based on such a change in the distance between the detection surface and the detection surface. In this case, since the detection surface and the detection surface are each formed by a substantially cylindrical side surface, regardless of the direction of the externally applied physical quantity, they are substantially the same with respect to the action direction of the physical quantity. The distance between the detection surface and the detection surface changes by the amount, and thus the mechanical amount can be detected isotropically.

The beam portion is formed by etching a thin film for a sacrificial layer formed on a supporting substrate, and the beam portion has a spiral shape having a planar shape having an overlapping portion. Therefore, when etching the sacrificial layer thin film, as described in the section (Problems to be Solved by the Invention), when the etchant enters between the overlapping portions in the beam, Due to the accompanying surface tension, the weight movable electrode is rotated around the anchor portion, and there is a possibility that adjacent beam portions adhere to each other. However, according to the fifth aspect of the present invention, since the rotation range limiting means for limiting the range in which the weight movable electrode can rotate around the axis perpendicular to the support substrate is provided, the rotation of the weight movable electrode is performed. There is no danger that adjacent beam portions will adhere to each other. As a result, while the spiral beam for supporting the weight movable electrode is formed by etching the thin film for the sacrificial layer, an adhesion phenomenon between the beams can be prevented beforehand. It is possible to improve the yield at the time of manufacturing the sensor.

According to the sixth aspect of the present invention, since the weight movable electrode is formed in a ring shape, the inner and outer regions thereof can be effectively used, and the entire area can be reduced.

According to the seventh aspect of the present invention, since the anchor portion is arranged inside the annular movable movable electrode, it is necessary to prepare a special area separately for disposing the anchor portion. And the overall area can be reduced. According to the eighth aspect of the present invention, since the fixed electrode is arranged inside the annular movable weight electrode, it is not necessary to prepare a special area separately for the arrangement of the fixed electrode, and the entire structure is eliminated. Can be reduced.

According to the ninth aspect of the present invention, when the physical quantity is not applied to the weight movable electrode, the distance between the detection surface and the detection surface is kept substantially uniform. Even when the voltage is applied from any direction substantially parallel to the surface of the support substrate, the amount of change in the distance between the detection surface and the surface to be detected is at substantially the same level as the magnitude of the applied mechanical quantity, As a result, isotropic mechanical quantity detection can be performed reliably and with substantially the same sensitivity.

According to the tenth aspect of the present invention, the detecting means is configured to detect contact between the detection surface of the weight movable electrode and the detection surface of the fixed electrode, so that a physical quantity of a predetermined level or more is obtained. The applied state can be reliably detected.

According to the twelfth aspect of the present invention, a plurality of electrode surfaces each having a predetermined distance from the detection surface of the weight movable electrode are provided at each position between the plurality of fixed electrodes. Since the sensitivity adjustment fixed electrode is provided, by changing the potential difference applied between the detection surface of the weight movable electrode and the electrode surface of the sensitivity adjustment fixed electrode, it acts between the detection surface and the electrode surface. The magnitude of the electrostatic force can be adjusted, and based on this, the sensor sensitivity can be adjusted with high accuracy.

According to the thirteenth aspect of the present invention, in the case where the fixed electrode for sensitivity adjustment is provided as described above, the plurality of fixed electrodes dispersedly arranged are opposed to the detection surface of the weight movable electrode. Is provided with a plurality of contact protrusions protruding in the direction of the detection surface, so that a state in which a mechanical amount of a predetermined level or more is applied is changed according to the contact between the detection surface of the weight movable electrode and the contact protrusion. It becomes possible to reliably detect. In addition, according to this configuration, when the weight movable electrode is displaced, there is no possibility that the detection surface comes into contact with a portion other than the fixed electrode, and as a result, a decrease in detection accuracy can be prevented.

According to the fourteenth aspect of the present invention, the rotation range restricting means is constituted by the contact projection and the concave portion formed so that the contact projection enters the weight movable electrode side. Thus, the shape of the rotation range limiting means can be simplified, and the manufacturability is improved.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment in which the present invention is applied to a semiconductor acceleration sensor will be described with reference to FIGS. FIG. 1 is a cross-sectional view of the semiconductor acceleration sensor, and FIG. 2 is a schematic cross-sectional view taken along line AA in FIG. 1 and 2, a semiconductor acceleration sensor (hereinafter simply referred to as an acceleration sensor) 11 as a physical quantity sensor is basically formed in the same shape as a support substrate 12 and an anchor portion 13 each made of single crystal silicon. For example, it is configured as a switch-type sensor having two beam portions 14 and 15, a weight movable electrode 16 (movable portion), and a fixed electrode 17.

The anchor portion 13 is formed in a cylindrical shape, and is fixed to a central portion on the support substrate 12 via a support anchor 18a to be described later. The beam portions 14 and 15 are formed in a spiral shape having portions where their planar shapes overlap with each other. One end of each of the beam portions 14 and 15 is integrally connected to a point symmetrical position on the peripheral wall of the anchor portion 13, thereby supporting the beams. It is supported in a form extending in a direction substantially parallel to the surface of the substrate 12. In this case, the beam 14
And 15, the ratio of the vertical dimension to the horizontal dimension of the vertical cross-sectional shape is set to be sufficiently large, and is configured to be elastically deformable in a direction substantially parallel to the surface of the support substrate 12.

The weight movable electrode 16 is formed in a ring shape (short cylindrical shape), and its inner peripheral surface is integrally connected to the free ends of the beams 14 and 15 so that the weight movable electrode 16 is formed on the support substrate 12. Are held parallel to the surface of the supporting substrate 12 at a predetermined interval, and freely displaced in a two-dimensional plane direction parallel to the supporting substrate 12 in response to application of an acceleration which is a mechanical quantity. In this case, the weight movable electrode 16
The detection surface 16a has a cylindrical outer peripheral surface, that is, a substantially cylindrical side surface in a direction perpendicular to the support substrate 12.

The fixed electrode 17 has an area corresponding to the weight movable electrode 16 and has a hollow cylindrical shape, and is fixed to a peripheral portion of the support substrate 12 via a support anchor 18b to be described later. In addition, the fixed electrode 17 has a cylindrical inner peripheral surface, that is, a substantially cylindrical side surface facing the detection surface 16a of the weight movable electrode 16 with a predetermined gap as a detection surface 17a. In this case, the distance between the detection surface 16a and the surface to be detected 17a is maintained to be substantially uniform when no acceleration is applied to the weight movable electrode 16, whereby the detection surface 1
The gap between 6a and the surface to be detected 17a has an annular shape with the same width.

The anchor 13, the beams 14 and 1
5. The weight movable electrode 16 and fixed electrode 17 have their resistances introduced by introducing impurities such as phosphorus into at least their surfaces or by depositing a conductive material on their surfaces by means of vapor deposition or plating. We try to reduce the rate.

The acceleration sensor 11 has a rotation range limiting means (for limiting the range in which the weight movable electrode 16 can rotate around an axis perpendicular to the support substrate 12 (the center axis of the anchor 13). As a rotation restricting means), for example, four through holes 19 formed in the weight movable electrode 16 and projectingly formed in the support substrate 12, so that a total of four through holes 19 are positioned so as to enter the respective through holes 19. A stopper shaft 20 is provided.

The four through holes 19 correspond to point symmetric positions on the weight movable electrode 16 (positions each having an opening angle of 90 ° with respect to the center of the weight movable electrode 16).
It has a hollow cylindrical shape in a direction perpendicular to 2. The four stopper shafts 20 are formed in a columnar shape, and are fixed on the support substrate 12 via a support anchor portion 18c described later.

In this case, as shown in an enlarged manner in FIG. 3, the through holes 19 and the stopper shafts 20 each having a circular cross-sectional shape are provided so as to be concentrically arranged. d2 is the detection surface 16a of the weight movable electrode 16.
The gap movable electrode 1 is larger than the gap dimension d1 between the fixed electrode 17 and the detection surface 17a (d2> d1).
6 is an axis perpendicular to the support substrate 12 (anchor 13
Of the beams 14 and 1
5 is set to a value such that adjacent portions do not contact each other.
As a result of such dimension setting, when the weight movable electrode 16 is rotated around an axis perpendicular to the support substrate 12,
As the stopper shaft 20 comes into contact with the inner peripheral surface of the through hole 19, the rotation of the weight movable electrode 16 is restricted, and the detection is performed due to the presence of the through hole 19 and the stopper shaft 20. The situation in which the contact between the surface 16a and the detected surface 17a is hindered does not occur.

In this embodiment, the cross-sectional shapes of the through hole 19 and the stopper shaft 20 are both circular. However, the function of limiting the rotation range of the weight movable electrode 16 as described above is satisfied. If there is, it is not limited to this. For example, the cross-sectional shape of the through hole 19 may be elliptical or rectangular, and the cross-sectional shape of the stopper shaft 20 can be freely changed. Further, at least one pair of the through hole 19 and the stopper shaft 20 may be provided.

FIGS. 4 to 10 schematically show the manufacturing process of the acceleration sensor 11, which will be described below with reference to FIG. First, as shown in FIG. 4, a single crystal silicon substrate 21 is prepared, and an alignment groove 21a is formed in the single crystal silicon substrate 21 by trench etching. Thereafter, a silicon oxide film 22 as a thin film for a sacrificial layer is formed on the entire region of the single crystal silicon substrate 21 including the groove 21a by a CVD method or the like.

Next, processing is performed to a state as shown in FIG. Specifically, first, a silicon nitride film 23 serving as an etching stopper at the time of etching the sacrificial layer is formed on the silicon oxide film 22. Then, the silicon nitride film 2
An opening having a shape corresponding to the region where the support anchors 18a to 18c are formed is formed by subjecting the stacked body of the silicon oxide film 3 and the silicon oxide film 22 to dry etching or the like via photolithography. Thereafter, a polysilicon thin film 24 is formed on the silicon nitride film 23 so as to fill the opening, and impurities are introduced into the polysilicon thin film 24 during or after the film formation by phosphorus diffusion or the like. This imparts conductivity. Further, by patterning the polysilicon thin film 24 using a photolithography technique, the base pattern of the support anchors 18a and 18b, and finally the weight movable electrode 16
Lower electrode 25 which is configured to face from below
(Including the base of the support anchor 18c), and a wiring pattern (not shown) for connecting the lower electrode 25 and the base pattern of the support anchor 18a. Thereby, as described later, the weight movable electrode 16 and the lower electrode 25 are in a state of being electrically connected to each other (that is, in an equipotential state).

Thereafter, as shown in FIG. 6, a silicon nitride film 26 is formed so as to cover the silicon nitride film 23 and the polysilicon thin film 24. Further, as shown in FIG. 7, a silicon oxide film 27 functioning as an insulating separation film is formed on the silicon nitride film 26, and a polysilicon thin film 28 as a bonding thin film is formed on the silicon oxide film 27. The surface of the polysilicon thin film 28 is planarized by chemical mechanical polishing or the like.

Next, processing is performed to a state as shown in FIG. Specifically, first, a support substrate 12 made of single crystal silicon is prepared, and the surface of the support substrate 12 and the surface of the polysilicon thin film 28 on the side of the single crystal silicon substrate 21 are subjected to hydrophilization treatment. Paste on the surface of chemical treatment. Then, the single-crystal silicon substrate 21 and the support substrate 12 are turned over and the single-crystal silicon substrate 2
The single crystal silicon substrate 21 is thinned by performing chemical mechanical polishing or the like on one side. At this time, the trench 21 previously trench-etched in the single crystal silicon substrate 21 is formed.
The silicon oxide film 22 in a can function as a polishing stopper for detecting completion of polishing. It is not necessary to use a high-quality single-crystal silicon substrate as the material of the support substrate 12.

Thereafter, as shown in FIG. 9, by forming an aluminum thin film on the single crystal silicon substrate 21 and then patterning, aluminum electrodes 29a and 29b for wire bonding are formed. In this case, the aluminum electrode 29a is formed so as to be finally located on the anchor portion 13, and the aluminum electrode 29b is finally formed on the fixed electrode 1
7 is formed. The aluminum electrode 29b is formed, for example, in an annular shape so as to be arranged in a uniformly distributed manner on the fixed electrode 17.

Then, as shown in FIG. 10, the single crystal silicon substrate 21 is subjected to trench etching through photolithography, so that the anchor portion 13 and the beam portion 1 are formed.
4 and 15, the structure for the weight movable electrode 16 and the fixed electrode 17, the through hole 19, and the stopper shaft 20 are formed.

Thereafter, the silicon oxide film 22 is removed with a hydrofluoric acid-based etchant to release the beams 14, 15 and the weight movable electrode 16 to form a movable structure, as shown in FIG. The basic structure of the acceleration sensor 11 having a complicated sectional shape is completed. That is, the silicon oxide film 22 serving as the sacrificial layer thin film is wet-etched, so that the beam portions 14 and 1
The weight movable electrode 16 in a form supported by the support 5 is formed. At this time, during the drying process after the sacrifice layer etching, the weight movable electrode 16 and the beam portions 14 and 15 become the supporting substrate 12
In order to prevent the situation of sticking to the side, a sublimant such as paradichlorobenzene is used.

The supporting anchors 18a to 18c are made of a polysilicon thin film 2 resistant to a hydrofluoric acid-based etching solution.
4, the etching is stopped at the support anchors 18a to 18c at the time of etching the sacrificial layer as described above, so that there is no variation in the etching state. Therefore, when etching the sacrificial layer, there is no need to precisely control the concentration and temperature of the hydrofluoric acid-based etchant or to perform strict time control for controlling the end time of the etching. Become.

After the basic structure of the acceleration sensor 11 is completed in this way, although not specifically shown, the weight movable electrode is formed by wire bonding between the aluminum electrodes 29a and 29b and the external connection terminals. The acceleration sensor 11 is finally completed by applying a potential difference between the fixed electrode 16 and the fixed electrode 17 and performing post-processing such as packaging.

The acceleration sensor 11 configured as described above
Are connected as shown in FIG. That is, in FIG. 11, the ground potential is applied to the anchor portion 13 and the output voltage V0 of the voltage source E is applied to the fixed electrode 17 in the detection circuit 30 (corresponding to the detection means in the present invention). Connected to be applied through As a result, in the steady state, a potential difference corresponding to the voltage V0 is applied between the weight movable electrode 16 and the fixed electrode 17 via the anchor portion 13 and the beam portions 14 and 15.

From such a steady state, the acceleration sensor 1
When an acceleration including a component parallel to the surface of the support substrate 12 is applied to the weight 1, the weight movable electrode 16 is displaced in a two-dimensional plane direction parallel to the support substrate 12, and the detection surface 16 of the weight movable electrode 16 Detected surface 17a of fixed electrode 17
And the distance between them will change. When the applied acceleration exceeds a certain level determined by the physical constants of the beams 14, 15 and the weight electrode 16, the detection surface 16a and the detection surface 17a come into contact with each other and a current flows. The detection by 30 makes it possible to detect an acceleration exceeding a certain level. in this way,
Since the detection circuit 30 is configured to detect the contact between the detection surface 16a and the detection surface 17a, it is possible to reliably detect a state where an acceleration of a certain level or more is applied.

In this case, since the detection surface 16a and the detection surface 17a are each formed by substantially cylindrical side surfaces, regardless of the direction of externally applied acceleration, the detection surface 16a and the detection surface 17a have a Thus, the distance between the detection surface 16a and the detection surface 17a changes by almost the same amount, and thus the acceleration can be detected isotropically. In particular, in this embodiment, the weight movable electrode 1
In a steady state where no acceleration is applied to the detection surface 6,
Since the distance between the detection surface 16a and the surface to be detected 17a is kept substantially uniform, even if acceleration is applied from any direction substantially parallel to the surface of the support substrate 12, the detection surface 16a The amount of change in the distance to the detection surface 17a is substantially the same level as the magnitude of the applied acceleration, and as a result, isotropic acceleration detection can be performed reliably and with substantially the same sensitivity. become. Moreover, the beams 14, 15
Since the planar electrode is formed in a spiral shape having an overlapping portion and is provided so as to be elastically deformable in a direction parallel to the surface of the support substrate 12, the movable electrode 16 is sensitively displaced when an acceleration is applied. And the sensitivity can be improved.

The beams 14 and 15 are formed by wet-etching a silicon oxide film 22 (a thin film for a sacrificial layer) formed on the supporting substrate 12 and have a planar shape. Are formed in a spiral shape having an overlapped portion. Therefore, when the silicon oxide film 22 is wet-etched, as described in the section of (Problems to be Solved by the Invention),
When the etchant intrudes between the overlapping portions 4 and 15, the weight movable electrode 16 is rotated around the anchor portion 13 by the surface tension accompanying the etching solution, and the adjacent beam portions 14 and 15 can adhere to each other. There is. In this embodiment, in order to prevent such a situation from occurring as much as possible, a sublimant such as paradichlorobenzene is used at the time of etching the sacrificial layer. However, in practice, the use of such a sublimation agent is not sufficient, and a situation in which the beam portions 14 and 15 adhere to each other due to water flow, water pressure, and the like accompanying repeated liquid exchange often occurs. .

In order to cope with such a situation, in this embodiment, the range in which the weight movable electrode 16 can rotate around the axis perpendicular to the support substrate 12 is determined by setting the beam portions 14 and 15 between adjacent portions. A through hole 19 and a stopper shaft 20 are provided to limit contact with each other.
As a result of this configuration, there is no possibility that the adjacent beam portions 14 and 15 adhere to each other due to the rotation of the weight movable electrode 16 at the time of etching the sacrificial layer or the like. That is, the spiral beam portions 14 and 15 for supporting the weight movable electrode 16 are replaced with the silicon oxide film 2 which is a thin film for a sacrificial layer.
Although the structure is formed by wet etching of No. 2, it is possible to prevent the adhesion phenomenon between the beam portions 14 and 15 beforehand, so that the yield in manufacturing the acceleration sensor 11 can be improved. Become.

Even when the beams 14 and 15 do not adhere to each other as described above, the beams 14 and 15 are rotated by the rotation of the weight movable electrode 16 due to the action of surface tension.
However, according to the present embodiment, it is possible to surely prevent the detection sensitivity from being affected as described above.

Of course, a situation in which a rotational force acts on the weight movable electrode 16 by the action of the surface tension as described above may occur even when the acceleration sensor 11 is actually used. Also, the adjacent beam portions 14 and 15 adhere to each other, or the beam portions 14 and 15
Does not change, so that the effect on the sensor sensitivity can be suppressed.

In this case, since the stopper shaft 20 as the rotation restricting means is located at a portion where a part of the weight movable electrode 16 is removed, the stopper shaft 20 is provided as a sensor while being provided with the rotation restricting means. There is no danger that the area efficiency of the device will deteriorate. Moreover, the weight movable electrode 16
Since the stopper shaft 20 and the stopper shaft 20 are formed of the same material (single-crystal silicon), they can be easily manufactured.

In this embodiment, the supporting substrate 12
On the side, there is provided an annular lower electrode 25 having a form opposed to the weight movable electrode 16 from below, and the weight movable electrode 16 and the lower electrode 25 are connected to the beams 14, 15, the anchor 13, the support anchor 18a, It is configured to be electrically connected via a wiring pattern (not shown) to have an equal potential. As a result of this configuration, it is possible to avoid a situation in which the weight movable electrode 16 adheres to the support substrate 12 due to the electrostatic force between the weight movable electrode 16 and the support substrate 12, and thus the operation reliability of the acceleration sensor 11 can be reduced. You can improve the nature.

In the above embodiment, the weight movable electrode 16
In order to provide a potential difference between the fixed electrode 17 and the fixed electrode 17, wire bonding means is used. However, a configuration in which a wiring pattern is formed using the polysilicon thin film 24 into which impurities are introduced, specifically, polysilicon When patterning the thin film 24 (see FIG. 5), the support anchors 18a
And a pair of wiring patterns for connecting the base patterns 18b and 18b to different external connection terminals are not required to use the above-described wire bonding means. Normally, an electrode pad for wire bonding needs to have a size of about 200 μm. However, if the internal wiring pattern as described above is used, the diameter of the upper surface of the anchor portion 13 is reduced from tens of μm to tens of Since the size can be reduced to about μm, the acceleration sensor 11 can be downsized.

Further, since the weight movable electrode 16 is formed in a ring shape, the inner and outer regions thereof can be effectively used, and the entire area can be reduced. In particular, in this embodiment, since the anchor portion 13 and the beam portions 14 and 15 are arranged inside the annular weight movable electrode 16, there is no need to prepare a special region separately, and the entire area is reduced. This can be effectively reduced, and the area efficiency as a sensor is improved.

(Second Embodiment) FIG. 12 shows a second embodiment of the present invention.
Only parts different from the embodiment will be described. That is, the acceleration sensor 11 ′ according to the second embodiment includes a support anchor 31 a, 3 made of a silicon oxide film formed on the support substrate 12.
1b and 31c, the anchor portion 13, the fixed electrode 1
7 and the stopper shaft 20 are respectively supported.

(Third Embodiment) FIGS. 13 to 16
Shows a third embodiment of the present invention. Hereinafter, this will be described focusing on differences from the first embodiment. FIG.
3 is a cross-sectional view of the semiconductor acceleration sensor, and FIG. 14 is a schematic cross-sectional view taken along line BB in FIG. 13 and 14
In the first embodiment, a semiconductor acceleration sensor (hereinafter, simply referred to as an acceleration sensor) 32 as a physical quantity sensor includes a support substrate 12, an anchor portion 13, two beam portions 14, 15. A switch-type sensor including, for example, eight sensitivity adjustment fixed electrodes 33 to 40 and fixed electrodes 41 to 48 each made of the same single crystal silicon as those structures in addition to the weight movable electrode 16. (These electrodes 33 to 40, 41 to 48
Are the same material, but are hatched differently in FIGS. 13 and 14 in consideration of the visibility of the drawings.) In particular, also in the present embodiment, the weight movable electrode 16 is formed on the weight movable electrode 16 as rotation range limiting means (rotation limiting means) for limiting a range in which the weight movable electrode 16 can rotate around an axis perpendicular to the support substrate 12. For example, four through-holes 19 and a total of four stopper shafts 20 protrudingly formed in the support substrate 12
Are provided, but it is sufficient that at least one pair of these is provided.

The sensitivity-adjusting fixed electrodes 33 to 40 have a shape in which the area corresponding to the weight movable electrode 16 is hollowed out in a cylindrical shape, and the area corresponding to the fixed electrodes 41 to 48 is hollowed out in a rectangular shape. Are arranged at equal intervals in a form surrounding the weight movable electrodes 16. In this case, each of the sensitivity adjustment fixed electrodes 33 to 40 has a surface facing the detection surface 16a of the weight movable electrode 16 on the electrode surface 3.
3a to 40a, and these electrode surfaces 33a to 40a
Are set so that their areas are equal to each other.

The fixed electrodes 41 to 48 are positioned at rectangular portions formed between the sensitivity adjusting fixed electrodes 33 to 40, and are arranged at equal intervals in a form surrounding the weight movable electrode 16. Distributed. In this case, a film or gap is formed between the fixed electrodes 41 to 48 and the sensitivity adjustment fixed electrodes 33 to 40 to separate them from each other. Further, contact protrusions 41a to 48a protruding in the direction of the detection surface 16a are integrally formed at portions of the fixed electrodes 41 to 48 facing the detection surface 16a.

In this case, the distance between the detection surface 16a and the contact protrusions 41a to 48a is maintained to be substantially uniform when no acceleration is applied to the weight movable electrode 16. In addition, the sensitivity adjustment fixed electrode 3
3 to 40 and fixed electrodes 41 to 48,
Similarly to the beams 14 and 15, and the weight movable electrode 16, in the manufacturing process of the acceleration sensor 32, an impurity such as phosphorus is introduced, or a conductive material is formed on the surface by deposition or plating. Has lowered the resistivity.

Further, in this embodiment, the support anchors 49a made of a silicon oxide film formed on the support substrate 12 are provided.
The anchor portions 13, the fixed electrodes 41 to 48 and the stopper shaft 20 are supported by 49 b and 49 c, respectively, and the sensitivity adjusting fixed electrodes 33 to 3 are respectively supported by support anchors (not shown) made of a silicon oxide film similarly formed on the support substrate 12. 40 is supported. further,
An aluminum electrode 29c for wire bonding is formed on the fixed electrodes 41 to 48, and the sensitivity adjustment fixed electrode 33 is formed.
40 to 40, an aluminum electrode (not shown) for wire bonding is formed.

As shown in FIG. 15 in an enlarged manner, the through hole 19 and the stopper shaft 20 are provided so as to be arranged concentrically as in the first embodiment, and the distance d2 between them is equal to the weight. The detection surface 16a of the movable electrode 16 and the fixed electrodes 41 to 48
Gap dimension d3 between contact projections 41a to 48a
When the weight movable electrode 16 is rotated around an axis perpendicular to the support substrate 12 (the center axis of the anchor portion 13), the beam portions 14 and 15 contact each other at adjacent portions when the weight movable electrode 16 is larger (d2> d3). Set to a value that does not. As a result of such a dimension setting, when the weight movable electrode 16 is rotated around an axis perpendicular to the support substrate 12, the stopper shaft 20 comes into contact with the inner peripheral surface of the through hole 19. The rotation of the weight movable electrode 16 is restricted, and the contact between the detection surface 16a and the contact protrusions 41a to 48a is hindered due to the existence of the through hole 19 and the stopper shaft 20. Will not be invited.

In this embodiment, the cross-sectional shape of both the through hole 19 and the stopper shaft 20 is circular. However, the function of limiting the rotation range of the weight movable electrode 16 as described above is satisfied. However, it is not limited to this. For example, the cross-sectional shape of the through hole 19 may be elliptical or rectangular, and the cross-sectional shape of the stopper shaft 20 can be freely changed.

The acceleration sensor 32 configured as described above
Are connected as shown in FIG. That is, in FIG. 16, the ground voltage is applied to the anchor portion 13, and the output voltage V 0 of the voltage source E is applied to the fixed electrodes 41 to 48.
Connected to be applied through Further, the output voltage V of the variable voltage source E 'is applied to the sensitivity adjustment fixed electrodes 33-40.
Connected so that R is applied. Thus, in the steady state, the weight movable electrode 16 and the fixed electrodes 41 to 41
48, a potential difference corresponding to the voltage V0 is applied through the anchor portion 13 and the beam portions 14 and 15, and a potential difference corresponding to the voltage VR is applied between the weight movable electrode 16 and the sensitivity adjustment fixed electrodes 33 to 40. Part 13 and beam part 14,
15.

At this time, the output voltage VR of the variable voltage source E '
Is adjusted, the detection surface 16a of the weight movable electrode 16 and the electrode surfaces 33a of the sensitivity adjustment fixed electrodes 33 to 40 are adjusted.
This makes it possible to adjust the magnitude of the electrostatic force acting between the acceleration sensor 32a and 40a, whereby the sensitivity of the acceleration sensor 32 can be adjusted with high accuracy.

In this embodiment having the above-described structure, when an acceleration exceeding a certain level is applied to the acceleration sensor 32 from the steady state, any one of the detection surface 16a and the contact protrusions 41a to 48a ( (One or two) and a current flows, and by detecting this current by the detection circuit 30, it is possible to reliably detect an acceleration exceeding a certain level.

Also in this embodiment, the through hole 19 and the stopper shaft 20 for limiting the range in which the weight movable electrode 16 can rotate around the axis perpendicular to the support substrate 12 are provided.
Is provided, the adjacent beam portions 14 and 1 are rotated by the rotation of the weight movable electrode 16 during the manufacturing process.
There is no possibility that the members 5 adhere to each other, and the yield in manufacturing the acceleration sensor 32 can be improved. Furthermore, in this embodiment, since the contact projections 41a to 48a projecting from the fixed electrodes 41 to 48 are arranged at equal intervals around the weight movable electrode 16, when the weight movable electrode 16 is displaced. , Where the detection surface 16a is a portion other than the fixed electrodes 41 to 48 (the fixed electrode 33 for sensitivity adjustment).
The possibility of contact with the electrode surfaces 33a to 40a) is eliminated. As a result, it is possible to prevent the detection accuracy from being lowered.

In the third embodiment, the sensitivity adjusting electrodes 33 to 40 and the fixed electrodes 41 to 4 which are respectively divided into eight parts.
Although the configuration is provided with 8, the configuration may be such that the number of divisions is changed. However, since the acceleration detection accuracy differs depending on the number of divisions, it is necessary to consider this. Further, it is preferable to set the numbers of the fixed electrodes and the contact projections so that the weight movable electrode does not come into contact with a portion other than the fixed electrode in order to ensure the sensing operation.

(Fourth Embodiment) FIGS. 17 and 18 show a fourth embodiment of the present invention in which the third embodiment is partially modified. Only parts different from the embodiment will be described. 17 is a cross-sectional view of the semiconductor acceleration sensor, and FIG. 18 is an enlarged cross-sectional view of a main part.

That is, the acceleration sensor 3 in this embodiment
Reference numeral 2 'denotes a rotation range restricting means for restricting a range in which the weight movable electrode 16 can rotate around an axis perpendicular to the support substrate 12, and is a means replacing the through hole 19 and the stopper shaft 20 in the third embodiment. It is characterized by having provided. Specifically, the rotation range restricting means in the present embodiment includes the contact projections 41 a ′ to the fixed electrodes 41 to 48.
48a ', and the contact projections 41a'-
48 a ′ and eight concave portions 50 formed on the outer peripheral surface of the weight movable electrode 16.

In this case, each recess 50 is formed in a rectangular shape into which the corresponding contact projection 41a'-48a 'is inserted. As shown in FIG.
The distance d4 (the distance in the diameter direction of the weight movable electrode 16) between the tip end surface of a ′ (〜48a ′) and the bottom of the concave portion 50 is
The gap dimension d5 between the detection surface 16a of the weight movable electrode 16 and the electrode surfaces 33 to 40a of the sensitivity adjustment fixed electrodes 33 to 40 is set to be smaller (d4 <d5). The distance d6 (the distance in the circumferential direction of the weight movable electrode 16) between the side surface of the contact projection 41a '(-48a') and the side of the recess 50 is determined by the weight movable electrode 16 with respect to the support substrate 12. When rotated around a vertical axis (the center axis of the anchor portion 13), the beam portions 14 and 15 are set to values at which adjacent portions do not contact each other.

As a result of such a dimension setting, when the weight movable electrode 16 is rotated around an axis perpendicular to the support substrate 12, the contact projections 41a 'with respect to the side of the recess 50.
48a ', the rotation of the weight movable electrode 16 is restricted and the recess 5
O and the presence of the contact projections 41a 'to 48a' do not cause a situation in which contact between the detection surface 16a and the contact projections 41a 'to 48a' is hindered. In particular, according to the present embodiment, the rotation range limiting means (contact projection 41)
Since the shapes of the a 'to 48a' and the recess 50) are simpler than the rotation range limiting means (the through hole 19 and the stopper shaft 20) in the first to third embodiments, the manufacturability is improved.

(Other Embodiments) The present invention is not limited to the embodiments described above, and the following modifications or extensions are possible. It is also possible to provide an anchor portion outside the annular weight movable electrode, support the weight movable electrode via the beam portion at this anchor portion, and arrange a fixed electrode inside the weight movable electrode. . According to this configuration, it is not necessary to separately prepare a special region for disposing the fixed electrode, and the entire area can be reduced. The number of beams is not limited to two as described in each embodiment. For example, three or more beams may be provided.
It can be done with a book.

In the case of a structure in which a fixed electrode having a planar detection surface is provided (a structure corresponding to the first and second embodiments), the detection surface of the movable weight electrode and the detection surface of the fixed electrode may be used. A configuration in which acceleration is sensed on the basis of a change in capacitance during the period is also possible. Further, the present invention is not limited to the acceleration sensor, and can be applied to a sensor that detects a dynamic quantity such as vibration.

Further, a configuration may be employed in which a metal film such as Au is formed on each surface of the weight movable electrode and the fixed electrode by vapor deposition or the like to detect a physical quantity. In this case, in order to avoid stress caused by a difference in thermal expansion coefficient between the metal and the semiconductor, it is desirable to form the metal film only at least at a portion where the weight movable electrode and the fixed electrode are in contact. In the acceleration sensor having a configuration in which a metal film is formed as described above, if the rotation restricting means according to the present invention is used, the metal films of the weight movable electrode and the fixed electrode can surely contact each other without shifting.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view taken along line AA in FIG.

FIG. 3 is an enlarged cross-sectional view of a main part.

FIG. 4 is a view schematically showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 5 is a view schematically showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 6 is a view schematically showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 7 is a view schematically showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 8 is a view schematically showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 9 is a view schematically showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 10 is a view schematically showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 11 is a diagram schematically showing a connection state;

FIG. 12 is a schematic longitudinal sectional view of a semiconductor acceleration sensor according to a second embodiment of the present invention.

FIG. 13 is a cross-sectional view of a semiconductor acceleration sensor according to a third embodiment of the present invention.

FIG. 14 is a schematic sectional view taken along line BB in FIG.

FIG. 15 is an enlarged cross-sectional view of a main part.

FIG. 16 is a diagram schematically showing a connection state;

FIG. 17 is a cross-sectional view of a semiconductor acceleration sensor according to a fourth embodiment of the present invention.

FIG. 18 is an enlarged cross-sectional view of a main part.

FIG. 19 is a diagram showing a cross-sectional structure of a conventional semiconductor acceleration sensor.

FIG. 20 is a diagram showing a vertical sectional structure of a conventional semiconductor acceleration sensor.

FIG. 21 is a diagram corresponding to FIG. 19 for describing a problem that occurs in a conventional semiconductor acceleration sensor.

[Explanation of symbols]

11, 11 'are semiconductor acceleration sensors (dynamic quantity sensors),
12 is a support substrate, 13 is an anchor portion, 14 and 15 are beam portions, 16 is a weight movable electrode (movable portion), 17 is a fixed electrode, 19 is a through hole (rotation range limiting means, rotation limiting means),
20 is a stopper shaft (rotation range limiting means, rotation limiting means), 22 is a silicon oxide film (thin film for a sacrificial layer), 30 is a detection circuit (detection means), 32 and 32 'are semiconductor acceleration sensors (dynamic quantity sensors), 33-40 are fixed electrodes for sensitivity adjustment, 33a-40a are electrode surfaces, 41-48 are fixed electrodes,
41a to 48a indicate contact projections, 41a 'to 48a' indicate contact projections (rotation range limiting means), and 50 indicate recesses (rotation range limiting means).

Claims (14)

[Claims] A movable portion supported by a beam portion extending from an anchor portion fixed on a support substrate; and a movable portion which is displaced in an arbitrary axial direction substantially parallel to the surface of the support substrate. A dynamic quantity sensor configured to detect a dynamic quantity acting on the movable part based on the rotation amount of the movable part, wherein a rotation restricting unit that restricts a rotational movement of the movable part in a plane parallel to the support substrate surface is provided on the support substrate. Characteristic physical quantity sensor. 2. The physical quantity sensor according to claim 1, wherein the rotation restricting means is formed at a position where a part of the movable portion is removed. 3. The beam section is formed in a spiral shape having an overlapping portion in a planar shape, and is provided so as to be elastically deformable in a direction parallel to a surface of the support substrate. 3. The dynamic quantity sensor according to claim 1, wherein the dynamic quantity sensor is formed in an annular shape having a detection surface composed of a substantially cylindrical side surface in a direction perpendicular to the direction of the axis. 4. The apparatus according to claim 1, wherein said movable portion and said rotation restricting means are made of the same material.
4. The physical quantity sensor according to any one of claims 3 to 3. 5. A supporting substrate, an anchor portion fixed on the supporting substrate, and a thin film for a sacrifice layer formed on the supporting substrate being etched so as to be floated from the supporting substrate. A beam portion which is provided and has a spiral shape having a planar shape having an overlapping portion, and one end of which is integrally connected to the anchor portion and is elastically deformable in a direction parallel to the surface of the support substrate, A detection surface formed of a substantially cylindrical side surface in a direction perpendicular to the support substrate, and being integrally connected to a free end side of the beam portion, a predetermined surface of the support substrate is provided on the support substrate; A weight movable electrode that is spaced and is held so as to be displaced in a direction parallel to the support substrate in response to the application of a mechanical quantity, and has a predetermined distance from the detection surface of the weight movable electrode on the support substrate. Facing And a fixed electrode having a surface to be detected consisting of a substantially cylindrical side surface facing the detection surface, and a distance change between the detection surface of the weight movable electrode and the detection surface of the fixed electrode. Detecting means for detecting the applied mechanical quantity based on the following formula: and rotation range limiting means for limiting a range in which the weight movable electrode can rotate around an axis perpendicular to the support substrate. Physical quantity sensor. 6. The physical quantity sensor according to claim 5, wherein the movable weight electrode is formed in an annular shape. 7. The physical quantity sensor according to claim 6, wherein
The annular weight movable electrode having a configuration provided with the detection surface on the outer peripheral surface thereof, and the anchor portion is disposed inside the weight movable electrode,
A physical quantity sensor, wherein the fixed electrode is arranged outside the weight movable electrode. 8. The physical quantity sensor according to claim 6, wherein
The annular weight movable electrode, the detection surface is provided on the inner peripheral surface thereof, and the anchor portion is disposed outside the weight movable electrode;
A physical quantity sensor, wherein the fixed electrode is arranged inside the weight movable electrode. 9. A distance between a detection surface of the weight movable electrode and a detection surface of the fixed electrode is kept substantially uniform in a state where no physical quantity is applied to the weight movable electrode. The physical quantity sensor according to any one of claims 5 to 8, wherein: 10. The dynamics according to claim 5, wherein said detecting means detects a contact between a detection surface of said weight movable electrode and a detection surface of said fixed electrode. Quantity sensor. 11. The physical quantity sensor according to claim 5, wherein the fixed electrodes are divided and arranged in a plurality of divided states. 12. The physical quantity sensor according to claim 11, further comprising an electrode surface facing the detection surface of the weight movable electrode at a predetermined interval at each position between the plurality of fixed electrodes. A dynamic quantity sensor comprising a plurality of fixed electrodes for sensitivity adjustment. 13. The physical quantity sensor according to claim 12, wherein the plurality of fixed electrodes dispersedly arranged have a plurality of contact points protruding in a direction facing the detection surface of the weight movable electrode. A physical quantity sensor comprising a projection. 14. The physical quantity sensor according to claim 13, wherein the rotation range restricting means is constituted by the contact protrusion and a concave portion formed so that the contact protrusion enters the weight movable electrode side. A physical quantity sensor characterized in that: