JPH11242053A - Semiconductor capacitance type multi-spindle acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor capacitance type multi-spindle acceleration sensor that can reduce the change in characteristic due to a temperature change. SOLUTION: A silicon substrate 3 where a movable electrode 6, a beam part 10, and a frame 3a are formed is arranged between first and second fixing substrates 1 and 2 and each substrate is joined. The movable electrode is connected in one piece via one edge 10a of the beam part. The beam part is separated from the frame, the other edge 10b of the beam part is formed thickly, and the other edge is joined to the first fixing substrate. Therefore, frame distortion being generated due to the difference in a temperature expansion rate with the first fixing substrate is not transferred to the beam part. Further, since the area of the other edge of the beam in contact with the first fixing substrate is small, the beam part cannot be generated greatly at the beam part. Therefore, the change in the tension of the beam part is reduced and the capacitance between the movable electrode and each fixing electrode does not change greatly due to a temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor capacitive multi-axis acceleration sensor used as an acceleration sensor mounted on, for example, a seismic sensor or an automobile.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show an example of a semiconductor capacitive multi-axis acceleration sensor. As shown in the figure, a silicon substrate 3 and an auxiliary substrate 4 are interposed between the upper and lower first fixed substrates 1 and the second fixed substrate 2. The first fixed substrate 1 and the auxiliary substrate 4 are formed of a glass substrate, and the second fixed substrate 2 is formed of a silicon substrate.

The silicon substrate 3 located on the upper side is shown in FIG.
As shown in (B), a weight 6 is connected to the inside of the frame 3a having a flat rectangular shape via a beam 5 having a substantially L-shape. Is elastically deformed, and the weight portion 6 is displaced in the direction of the acceleration. Further, an auxiliary weight 7 is attached to the lower surface of the weight 6 in order to improve sensitivity. The auxiliary weight 7 is formed by the auxiliary substrate 4.

On the lower surface of the first fixed substrate 1, four fixed electrodes 8a to 8d having the same shape are provided as shown in FIG.
Are formed. These four fixed electrodes 8a to 8d
Have substantially the same shape and the same area, and are arranged in parallel in the X-axis direction and the Y-axis direction. The fixed electrodes arranged in the respective axial directions serve as X-axis direction detection fixed electrodes or Y-axis direction detection fixed electrodes. further,
The surface of the weight portion 6 facing the fixed electrodes 8a to 8d becomes the movable electrode 9. The movable electrode 9 becomes a common electrode for each of the fixed electrodes 8a to 8d.

In such a configuration, in a normal state where the acceleration is 0, the weight portion 6 maintains a horizontal state, so that the distance between the four fixed electrodes 8a to 8d and the movable electrode 9 is constant.
Further, the overlapping area of each of the fixed electrodes 8a to 8d and the movable electrode 9 becomes equal. Therefore, the capacitance generated between the electrodes becomes equal. The direction connecting the fixed electrodes 8a to 8d and the movable electrode 9 (the vertical direction in FIG. 6) is defined as the Z axis, and the X axis is defined as the Y axis.
Assuming that the axes are in directions as shown in FIG. 6, if acceleration is applied only in the X-axis direction, the weights 6 and the auxiliary weights 7 receiving the acceleration try to move in the X-axis direction. Due to the structure, parallel movement is not possible, and the distance between the fixed electrodes 8a and 8b and the movable electrode 9 in the direction of the force is shortened.
Conversely, the distance between the fixed electrodes 8c and 8d and the movable electrode 9 increases. Similarly, if acceleration is applied only in the Y-axis direction, the distance between the fixed electrodes 8a, 8d and the movable electrode 9 becomes shorter, and conversely, the distance between the fixed electrodes 8b, 8c and the movable electrode 9 becomes longer.

Since the distance between the electrodes is different as described above, the capacitance generated between the electrodes also changes, and the pattern of the change differs depending on the direction in which the acceleration is applied.
By detecting the amount of change in capacitance generated between the electrodes, the direction and magnitude of the acceleration can be known.

If acceleration is applied only in the Z-axis direction, the movable electrode 9 serving as a common electrode and the fixed electrodes 8a to 8a
When the distance d is the same distance between the electrodes, the capacitance generated between the electrodes changes. Therefore, it is possible to know the direction and magnitude of the acceleration.

[0008]

However, in the above-described conventional semiconductor capacitance type multi-axis acceleration sensor, both surfaces of the frame 3a made of silicon are respectively joined to the first fixed substrate 1 and the auxiliary substrate 4 made of glass. Therefore, if the temperature changes, the frame 3a will be distorted due to the difference in the rate of temperature expansion between the substrates. Then, frame 3
The strain is transmitted to the beam part 5 formed integrally with
The tension of the beam 5 changes, and the position of the movable electrode 9 changes. Therefore, the movable electrode 9 and the fixed electrodes 8a to 8
Each capacitance between d changes.

Particularly, in the wafer bonding step of bonding the substrates, since a high temperature is applied to each substrate, distortion occurs in the frame 3a, which affects the tension of the beam portion 5, and the movable electrode 9, the fixed electrodes 8a to 8a. The sensor is manufactured in a state where the distance between 8d (the capacitance generated between the electrodes) is changed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has as its object to solve the above-described problems and to reduce variations in sensor characteristics and changes in characteristics. To provide a multi-axial acceleration sensor.

[0011]

In order to achieve the above-mentioned object, in a semiconductor capacitive multi-axis acceleration sensor according to the present invention, a fixed substrate having a plurality of fixed electrodes formed thereon and a semiconductor bonded to the fixed substrate are provided. Substrate, the semiconductor substrate includes a beam portion that elastically supports a movable portion that is displaced by receiving acceleration, and the movable electrode is provided with a predetermined gap on a surface of the movable portion facing the fixed electrode. It is assumed that a semiconductor capacitive multi-axis acceleration sensor is provided and detects acceleration in a plurality of directions based on the capacitance generated between the movable electrode and the fixed electrode. A thick portion is provided on a joint surface side of an end of the beam portion, and the thick portion is joined to a joint surface of the fixed substrate (claim 1).

Further, as another solution, under the same prerequisites as above, a concave portion is formed on the surface of the fixed substrate facing the movable electrode, and the plurality of fixed electrodes are formed on the bottom surface of the concave portion. The movable portion and the beam portion are formed integrally, and one end of the beam portion is connected to the fixed substrate to support the movable portion (claim 2).

As another solution, under the same precondition, the semiconductor substrate has a thick outer frame and a thin inner frame, and the outer frame and the inner frame are at least partially provided. Are separated by a slit, one end of the beam portion is connected to the movable portion,
The other end of the beam may be connected to the inner frame (claim 3).

According to the first and second aspects of the present invention, since the area of the end of the beam that comes into contact with the fixed substrate can be reduced, distortion generated in the beam is reduced. Therefore, even if a temperature change occurs, the tension of the beam portion does not change much, and the distance between the movable electrode and each fixed electrode does not change much. Therefore, no change occurs in the capacitance between the movable electrode and each fixed electrode.

According to the third aspect of the present invention, since the thin inner frame and the outer frame are at least partially separated into slits, distortion generated in the outer frame is not easily transmitted to the inner frame. In addition, since the inner frame is made thin, distortion is less likely to occur between the inner frame and the fixed electrode.
Therefore, the distortion transmitted to the beam portion is reduced, the tension of the beam portion does not change much, and the capacitance between the movable electrode and each fixed electrode does not change.

* Definition of terms The term "multi-axis" of the semiconductor capacitive multi-axis acceleration sensor described in this specification means a plurality of axes. Included.

The movable portion described in the claims corresponds to a weight portion in the embodiment. Further, another weight portion (auxiliary weight portion 7) or the like may be connected below the movable portion as in the embodiment. Further, a structure may be employed in which the volume of the movable part is reduced and the function of increasing the weight becomes less effective. In that case, it is possible to cope by connecting a separate weight portion like the auxiliary weight portion 7 described in the embodiment.

[0018]

FIG. 1 shows a first embodiment of a semiconductor capacitive multi-axis acceleration sensor according to the present invention. As shown in the figure, the basic structure is the same as the above-mentioned conventional one. That is, in order from the top, a first fixed substrate (glass substrate) 1, a silicon substrate 3, an auxiliary substrate 4 (glass substrate),
Four substrates are laminated so as to be a second fixed substrate (silicon substrate), and are joined around the outside.

On the lower surface of the first fixed substrate 1, four fixed electrodes 8a to 8d (only 8b and 8c are shown in FIG. 1, but as shown in FIG. 6) are provided. In addition, the silicon substrate 3 has the weights 6 and 6 formed by etching.
The beam part 10 and the frame 3a are formed. Weight part 6
Is formed so that the upper surface thereof is square, and is formed such that the area is gradually reduced below, and the upper surface becomes the movable electrode 9. Further, the auxiliary substrate 4 has an auxiliary weight portion 7 and a weight frame 4a formed by etching. The auxiliary weight 7 is separated from the weight frame 4a, and is connected to the lower surface of the weight 6, so that the movable electrode 6 has high accuracy in measuring the acceleration of the movable electrode 6. At this time, the lower surface side of the auxiliary weight portion 7 is shaved by etching and can move without contacting the second fixed substrate 2.

Here, in the present invention, the support structure of the weight portion 6 (movable electrode 9) through the beam portion 10 is improved. Specifically, the weight portion 6 is formed by four beam portions 10 having a substantially L-shape in a plane.
The support of the (movable electrode 9) is the same as that of the related art. One end 10 a of the beam 10 is connected to each of the four corners of the weight 6, and most of the beam 10 is adjacent to the weight 6. It is arranged parallel to the side. The other end 10 b of the beam 10 is connected to the lower surface of the first fixed substrate 1.
That is, the beam 10 is separated from the frame 3a.

Further, the movable electrode 9 on the upper surface of the weight portion 6 and
Between the fixed electrodes 8a to 8d on the lower surface of the first fixed electrode 1,
Since a predetermined gap needs to be provided, a space corresponding to the gap also exists between the upper surface of most of the beam portion 10 and the lower surface of the first fixed electrode 1. Therefore, in the present embodiment, the thickness of the other end 10b of the beam portion 10 is increased. The other end 1
The thickness 0b is formed to be equal to the gap between the movable electrode 9 and the fixed electrodes 8a to 8d when no acceleration is applied. The other end 10 of the beam 10
b are fixed electrodes 8a to 8d on the surface of the first fixed substrate 1.
Are connected to the unformed area. Therefore, the weight 6 (the movable electrode 9) is elastically supported by the first fixed substrate 1 via the beam 10.

Therefore, the first fixed substrate 1 is changed by the temperature change.
Even if distortion occurs in the frame 3a joined to the
Does not transmit distortion. Further, since the area of the other end 10b of the beam portion 10 in contact with the first fixed substrate 1 is small, the first
The distortion caused by the difference in the rate of thermal expansion from the fixed substrate 1 does not significantly affect the tension of the beam portion 10. Therefore, the position of the movable electrode 6 elastically supported via the beam portion 10 does not change much, and the capacitance between the movable electrode 6 and each of the fixed electrodes 8a to 8d maintains the reference value.

As a result, even when a high temperature is applied to each substrate during the manufacture of the sensor, there is no variation in the initial capacitance, and a stable product with no variation in the sensitivity of the sensor can be manufactured and supplied. it can.

FIG. 2 shows a second embodiment of a semiconductor capacitive multi-axis acceleration sensor according to the present invention. In this embodiment, a concave portion 12 is formed on the lower surface of the first fixed substrate 1 (on the side of the silicon substrate 3), and fixed electrodes 8a to 8d are formed on the bottom surface of the concave portion 12. The opening (planar shape) of the concave portion 12 is formed larger than the upper surface (the movable electrode 9) of the weight portion 6, and the movable electrode 6 is formed in the concave portion 12.
Is made displaceable.

In this embodiment, the upper surfaces of the weight 6 (the movable electrode 9) and the beam 10 are not etched.
It is formed so as to have the same height as the upper surface of the frame 3a. In this state, the frame 3a of the silicon substrate 3
It is joined to the outer periphery of the lower surface of the first fixed substrate 1 (FIG. 2).
A gap is formed between the movable electrode 9 and the fixed electrodes 8a to 8d depending on the depth of the recess 12 ((B) area indicated by middle hatching).

Further, the other end 10 b of the beam 10 supporting the weight 6 (movable electrode 9) is connected to the recess 12 of the first fixed substrate 1.
(The area shown by hatching in FIG. 2B) and supported. In this embodiment, the gap between the electrodes is formed by the concave portion 12 formed on the lower surface of the first fixed electrode 1, and the upper surface of the beam portion 10 and the upper surface of the silicon substrate 1 are flush. Therefore, the upper surface of the beam 10 also contacts the lower surface of the first fixed substrate 1. Therefore, an insulating film is formed on the upper surface of the beam portion 10 except for the upper surface of the other end 10b of the beam portion 10 serving as the connection portion. Thereby, the first fixed substrate 1 and the silicon substrate 3
Are subjected to anodic bonding, only the contact portions indicated by hatching in FIG.

Also in this embodiment, the first temperature is changed by the temperature change.
Since the strain generated in the frame 4a joined to the fixed substrate 1 is not transmitted to the beam 10, the tension of the beam 10 does not change much, and the capacitance of the movable electrode 6 and each of the fixed electrodes 8a to 8d does not change.

FIG. 3 shows a third embodiment of the semiconductor capacitive multi-axis acceleration sensor according to the present invention. This embodiment also has a four-layer structure in which a silicon substrate 3 and an auxiliary substrate 4 are arranged and joined between the first fixed substrate 1 and the second fixed substrate 2. Then, fixed electrodes 8 a to 8 d (only 8 b and 8 c are shown in FIG. 3) are provided on the lower surface of the first fixed electrode 1, a weight portion 6 having a movable electrode 9 is provided on the silicon substrate 3, and the auxiliary substrate 4 is provided on the auxiliary substrate 4. The structure for forming the auxiliary weight 7 connected to the lower surface of the weight 6 is the same as in the above embodiments.

Here, in this embodiment, more specifically, the structure for supporting the weight portion 6 (movable electrode 9) via the beam portion 10 'is improved from the structure of the silicon substrate 3. That is, first, a shallow first recess 14 is formed at the center of the upper surface of the silicon substrate 3, and the depth of the first recess 14 is fixed to the fixed electrode 8.
a to 8d and the gap between the movable electrode 9. A U-shaped slit 15 is formed so as to surround three sides of the first recess. Thus, the inner frame 16 existing between the slit 15 and the first recess 14 is cantilevered to the outer frame 17 via the connecting portion 18.

On the other hand, the lower surface of the silicon substrate 3
A second recess 19 is formed opposite to a position surrounding the periphery of the recess 14. The second recess 19 is provided with the slit 15
And the inside surrounded by the second recess 19 is the weight portion 6
Becomes

The weight portion 6 is formed separately inside the inner frame 16, and the weight portion 6 and the inner frame 1 are separated.
6 are elastically supported by four beam portions 10 '. This beam part 10 ′ is also formed in the first recess 14,
There is a predetermined space between the fixed electrode 1 and the lower surface. Also,
The specific shape of the beam portion 10 'is bent at a right angle along each vertex of the weight portion 6, and one end 1 of each beam portion 10' is formed.
0'a is connected to the center of each side of the weight 6 and the other end 10 '
b denotes the inner side of the inner frame 16 (the inner frame 16 facing the side of the movable electrode 6 to which one end 10'a is connected).
(A side orthogonal to the side inside).

The upper surfaces of the inner frame 16, the outer frame 17, and the connecting portion 18 are joined to the first fixed substrate 1. Thereby, the weight 6 (movable electrode 9)
Is connected to the first fixed electrode 1 via the beam 10 ′ and the inner frame 16. Therefore, even if the joint portion is distorted due to a difference in thermal expansion coefficient between the first fixed substrate 1 and the silicon substrate 3 due to a temperature change, the distortion is transmitted to the outer frame 17 but the inner frame 1
Since the second recess 15 is formed in the connection portion 6 and the connection portion 18 and is formed to be thinner than the outer frame 17, little distortion occurs. Further, the inner frame 16 is separated from the outer frame 17 by a slit 15,
Since the inner frame 16 is connected to the outer frame 17 via the relatively thin connecting portion 18, distortion generated in the outer frame 17 is not easily transmitted to the inner frame 16. Therefore, the strain is hardly transmitted to the beam portion 10 ′ integrally connected to the inner frame 16, so that the beam portion 10 ′ is not provided.
Does not change. Therefore, the distance between the gap between the movable electrode 9 and the fixed electrode 8 does not change due to the temperature change, so that the capacitance does not change, and even if a high temperature is applied during the manufacture of the sensor, the initial capacitance of the sensor varies. Absent.

FIG. 4 shows a semiconductor capacitive multi-axis acceleration sensor according to a fourth embodiment of the present invention. In this embodiment, the basic configuration is the same as that of the third embodiment. That is, the silicon substrate 3 and the auxiliary substrate 4 are arranged between the first fixed substrate 1 and the second fixed substrate 2, and have a four-layer structure in which the substrates are joined. The silicon substrate 3 has an outer frame 17 and an inner frame 16, and is the same in that the movable electrode 9 (weight 6) is supported by the four beams 10 ′ with respect to the inner frame 16. .

Here, in this embodiment, the shape of the slit 15 'formed between the inner frame 16 and the outer frame 17 is made into a flat square shape, and the inner frame 16 and the outer frame 1 are formed.
7 are separated. The inner frame 16 is connected to the block portion 20 via the connecting portion 18 in a cantilevered manner. The block section 20 is in contact with both the first fixed board 1 and the auxiliary board 4. Further, the upper surfaces of the inner frame 16, the outer frame 17, the connecting portion 18, and the block portion 20 are anodically bonded at contact portions with the lower surface of the first fixed substrate 1.

With this configuration, even if distortion occurs on the outer frame 17 side due to a temperature change, the distortion is not transmitted to the inner frame 16 side. Further, since the block portion 20 has a slender rectangular shape, and its area is sufficiently smaller than that of the outer frame 17, distortion generated in the block portion 20 when the temperature changes is small. further,
Since the second recess 19 is formed in the inner frame 16 and the connecting portion 18 and is formed to be thinner than the outer frame 17, little distortion occurs. Therefore, distortion generated or transmitted to the inner frame 16 side is smaller than that in the third embodiment.

Therefore, it is possible to suppress as much as possible the transmission of strain to the beam portion 10 ′ integrally connected to the inner frame 16, and it is possible to suppress a change in the tension of the beam portion 10 ′ due to a temperature change. . Therefore, the movable electrode 9 is changed by the temperature change.
The capacitance of the fixed electrodes 8a to 8d does not change, and even if a high temperature is applied during the manufacture of the sensor, the initial capacitance of the sensor does not vary. Note that the other configuration, operation, and effect are the same as those of the above-described embodiments (particularly, the third embodiment), and thus the same reference numerals are given and the detailed description is omitted.

[0037]

As described above, in the semiconductor capacitive multi-axis acceleration sensor according to the present invention, the frame and the beam portion to be joined to the first fixed substrate are separated, and the beam portion is connected to the first fixed substrate. Therefore, the strain generated in the frame having a large joint area with the first fixed substrate due to the temperature change is not transmitted to the beam.
In addition, since the area where the beam is joined to the first fixed substrate is small, distortion generated in the beam is small. Therefore, since the tension of the beam does not change much and the position of the movable electrode supported by the beam does not change, it is possible to prevent the capacitance between the movable electrode and the fixed electrode from changing. In particular, at the time of manufacturing the sensor, even if a high temperature is applied, the position of the movable electrode does not change, so that the initial capacitance of the sensor does not change.

[Brief description of the drawings]

FIG. 1A is a diagram for explaining a structure of a semiconductor capacitive multi-axis acceleration sensor according to a first embodiment of the present invention. (B) is a plan view at the BB 'position.

FIG. 2A is a diagram illustrating a structure of a semiconductor capacitive multi-axis acceleration sensor according to a second embodiment of the present invention. (B) is a plan view at the BB 'position.

FIG. 3A is a diagram illustrating a structure of a semiconductor capacitive multi-axis acceleration sensor according to a third embodiment of the present invention. (B) is a plan view at the BB 'position.

FIG. 4A is a view for explaining the structure of a semiconductor capacitive multi-axis acceleration sensor according to a fourth embodiment of the present invention; (B) is a plan view at the BB 'position.

FIG. 5A is a view for explaining the structure of a conventional semiconductor capacitive multi-axis acceleration sensor. (B) is the B-
It is a top view in the B 'position.

FIG. 6 is a diagram illustrating an example of a fixed electrode of a conventional semiconductor capacitive multi-axis acceleration sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st fixed substrate 2 2nd fixed substrate 3 silicon substrate 4 auxiliary substrate 6 weight part 7 weight part 8a, 8b, 8c, 8d fixed electrode 9 movable electrode 10 beam part 12 recessed part 16 inner frame 17 outer frame 18 connection part 20 support Department

Claims (3)

[Claims] 1. A semiconductor device comprising: a fixed substrate having a plurality of fixed electrodes formed thereon; and a semiconductor substrate joined to the fixed substrate, wherein the semiconductor substrate elastically supports a movable portion that is displaced by receiving acceleration. And a movable electrode is provided at a predetermined gap on a surface of the movable portion facing the fixed electrode, and acceleration in a plurality of directions is detected based on capacitance generated between the movable electrode and the fixed electrode. A multi-axis acceleration sensor comprising: a thick portion provided on a joint surface side of an end of the beam portion; and the thick portion is joined to a joint surface of the fixed substrate. Type multi-axis acceleration sensor. 2. A semiconductor device comprising: a fixed substrate on which a plurality of fixed electrodes are formed; and a semiconductor substrate bonded to the fixed substrate, wherein the semiconductor substrate elastically supports a movable portion which is displaced by receiving acceleration. And a movable electrode is provided at a predetermined gap on a surface of the movable portion facing the fixed electrode, and acceleration in a plurality of directions is detected based on capacitance generated between the movable electrode and the fixed electrode. A concave portion is formed on a surface of the fixed substrate facing the movable electrode, the plurality of fixed electrodes are formed on a bottom surface of the concave portion, and the movable portion and the beam portion are provided. Are connected integrally, one end of the beam portion is connected to the fixed substrate, and supports the movable portion. 3. A fixed substrate on which a plurality of fixed electrodes are formed, and a semiconductor substrate bonded to the fixed substrate, wherein the semiconductor substrate elastically supports a movable portion which is displaced by receiving acceleration. And a movable electrode is provided at a predetermined gap on a surface of the movable portion facing the fixed electrode, and acceleration in a plurality of directions is detected based on capacitance generated between the movable electrode and the fixed electrode. A semiconductor capacitive multi-axis acceleration sensor, wherein the semiconductor substrate has a thick outer frame and a thin inner frame, and the outer frame and the inner frame are
At least a part thereof is separated by a slit; one end of the beam portion is connected to the movable portion; and the other end of the beam portion is connected to the inner frame. .