JPH04169856A - Semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE:To enable the detection of three-dimensional acceleration at a high sensitivity with a small device by connecting a central thick part, a medium thick part and a medium thick part surrounding it at a specified interval and a peripheral thick part surrounding them at a specified interval with thin support parts separately. CONSTITUTION:For example, acceleration is applied in a direction (x), an inertial force works on a central thick part 5 and a medium thick part 6. As a (z) axis-wise deviation l is caused between a center of gravity G of the thick part 5 and thin support parts 9 and 11, a compression stress works on the support part 9 more with an access to a peripheral thick part 7 while a tension stress works thereon more with an access to the thick part 6. The compression stress and the tension stress work on the support part 11 in a full opposition to each other. So, a difference is determined between outputs of bridge circuits made up of strain gauges 2 and 4 as provided respectively on the support parts 9 and 11 to detect an electrical signal corresponding to acceleration working in the direction (x). Likewise, the acceleration working in the direction (y) is determined by measuring a difference of a stress working on thin support parts 8 and 10 as caused by an inertial force working on the thick part 5 with the strain gauges 1 and 3 to detect an electrical signal corresponding to the acceleration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a semiconductor acceleration sensor capable of detecting three-dimensional acceleration.

(Prior Art) As a conventional semiconductor acceleration sensor, there is, for example, one shown in FIG. 5 (see Japanese Patent Laid-Open No. 169078/1983). Here, Fig. 5) is a top view, and Fig. 5(b) is a sectional view taken along line BB in Fig. 5(a).

That is, the peripheral thick wall portion 21 is formed to surround the square central thick wall portion 20 at a predetermined distance 22 from the central thick wall portion 20 in a square shape. Central thick part 20
The peripheral thick portion 21 is connected and supported by thin support portions 23 to 26 on the same plane on the front side in two directions. Above each support section, strain gauge groups 16 to 19 consisting of four piezoresistors are placed.
is formed by diffusion, etc., and the c, y, and z components of stress caused by acceleration are detected.

(Problem to be Solved by the Invention) However, in such a conventional semiconductor device degree sensor, when the acceleration to be detected becomes small, the thin support part connecting and supporting the central thick part at at least four places Since the stress generated is also small, there is a limit to the accuracy of detection. In order to improve the accuracy of this detection, that is, to improve the sensitivity, it is necessary to increase the mass of the central thick part where the inertial force that causes the displacement for detection acts, thereby increasing the inertial force. As a result, there was a problem that the entire acceleration sensor became large.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor acceleration sensor that is small in size and has good sensitivity.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the semiconductor acceleration sensor of the present invention includes a thick central thick portion and a predetermined interval from the central thick portion. a thick intermediate thick part formed to surround the central thick part; and a thick intermediate thick part formed to surround the intermediate thick part at a predetermined distance from the intermediate thick part. a thin-walled first thin-walled support portion that connects the central thick-walled portion to the intermediate thick-walled portion and supports the central thick-walled portion at at least two locations on the same line as the peripheral thick-walled portion; A thin-walled portion that connects the intermediate thick-walled portion to the inside of the peripheral thickness and supports the intermediate thick-walled portion at two locations on the same line perpendicular to the straight line connecting the two first thin-walled support portions on the same line. It is characterized by having a second thin support part and a strain gauge formed above the first and second thin support parts.

(Function) According to the semiconductor acceleration sensor according to the present invention, when acceleration acts, the part on which the inertial force that causes the displacement for detection acts is the central thick part in one of the three detection directions. , and the other direction perpendicular to the − direction is an intermediate thick portion including the central thick portion. In addition, the first thin support part that connects and supports the central thick part and the second thin support part that connects and supports the middle thick part are only required at two locations in the detection direction, and only at two locations other than those two locations. In this case, the part where the inertial force acts is separated from the surroundings. Therefore, regarding detection in these two directions, the first and second thin supports forming the strain gauges on the upper side are easily displaced, and therefore better sensitivity can be obtained.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows an embodiment of a semiconductor acceleration sensor according to the present invention, in which the first image) is a top view, and FIG. 1(b) is a sectional view taken along the line A-A in the first image). The configuration will be explained below.

The intermediate thickness interior 6 is provided so as to surround the square central thick part 5 at a predetermined distance 13 from the central thick part 5 in a square shape.

This spacing 13 is easily formed by anisotropic etching, such as electric field etching. The central thick portion 5 and the intermediate thick portion 6 are located at two locations on the X axis in FIG.
It is connected and supported by a thin support part 8.10, which is a thin first support part, on the same plane in two directions.

Further, a peripheral thick wall portion 7 is provided so as to surround the middle thick wall portion 6 at a predetermined distance 12 from the middle thick wall portion 6 in a square shape. This interval 12 is also formed by the same method as the interval 13. The intermediate thick part 6 and the peripheral thick part 7 are located at two places on the X-axis perpendicular to the y-axis, and the thin support part 8.1 is located on the same plane in two directions.
Thin support parts 9, 1 as second thin support parts similar to 0
It is connected and supported by 1.

Above the four thin supports 8 to 11, there are provided strain resistance gauge groups 1 to 4 consisting of four strain resistance gauges which are piezoresistive elements formed by diffusion etc., and these strain resistance gauges The strain resistance gauges forming groups 1-4 are electrically connected to form a bridge circuit.

Next, the operation of the above embodiment will be explained.

When a force due to acceleration or the like is applied to the semiconductor acceleration sensor according to this embodiment, an inertial force acts on the central thick portion 5 and the intermediate thick portion 6, and the thin support portions 8 to 11 are displaced. An electrical signal is detected depending on this displacement state.

That is, the X direction will be explained with reference to FIG.

The semiconductor acceleration sensor according to this embodiment is installed on a pedestal 12 that supports only the peripheral thick walled portion 7 of the sensor, and when acceleration acts in the positive X direction, for example, the central thick walled portion 5
Inertial force acts on the intermediate thick portion 6, that is, the inner portion of the intermediate thick portion 6. Here, there is a misalignment between the center of gravity G of the central thick portion 5 and the thin support portions 9 and 11 in the z-axis direction. Due to this deviation, when the inertial force acts, compressive stress acts on the thin support portion 9 closer to the peripheral thick wall portion 7, and conversely, tensile stress acts on the thin wall support portion 9 closer to the intermediate thick wall portion 6. act. On the other hand, in the thin support portion 11, the closer it is to the peripheral thick wall portion 7, the more tensile stress acts on it, and the closer it is to the middle thick wall portion 6, the more compressive stress acts on it. Therefore, by taking the difference in the output signals of the bridge circuit formed by the strain gauge groups 2.4 provided on each of these thin-walled supports 9.11, an electrical signal corresponding to the acceleration acting in the X direction can be detected. be done.

Next, the X direction will be explained. Regarding the X direction, it is the same as the X direction; acceleration acts and inertial force acts on the central thick part 5, and by taking the difference in stress acting on the thin support part 8.10 due to this inertial force, An electrical signal corresponding to the applied acceleration is detected.

Finally, two directions will be explained with reference to FIGS. 3 and 4. For example, when acceleration acts in two negative directions, inertial force acts on the central thick portion 5 and the intermediate thick portion 6. Due to this inertial force, the outer side of the four thin-walled supports 8 to 11, that is, the closer the thin-walled supports 8 and 10 are to the intermediate thick-walled portion 6, and the peripheral thick-walled portions Tensile stress acts on the inner side, that is, the closer the thin support parts 8 and 10 are to the central thick part 5, and the closer to the middle thick part 6 of the thin support parts 9 and 11, the more compressive stress is applied. Stress acts. Here, since the inertial force that acts on the thin support parts 8, 10 and the thin support parts 9, 11 is not necessarily the same, the magnitude of the stress that acts on them is also not the same. Therefore, by taking the average or sum of the output signals of the bridge circuits of strain gauge groups 1 and 3, and the average or sum of the output signals of the bridge circuits of strain gauge groups 2 and 4, the An electrical signal is detected.

In this way, according to the semiconductor acceleration sensor according to this embodiment, the X-direction component of acceleration is expressed as a twist around the y-axis.
The direction component is the twist around the X axis, and the two-way acid content is 2
As a force acting in a direction, three-dimensional acceleration can be effectively detected.

Furthermore, for example, in detecting the X-direction component of acceleration,
Conventionally, at least four thin-walled support parts (thin-walled support parts 23 to 26 in FIG. 5) were required to support the part on which inertial force acts, but especially in the case of the semiconductor acceleration sensor according to this embodiment, this is necessary. are located at only two locations on the X-axis (the thin-walled support portions 9 and 11 in FIG. 1), and by separating the thin-walled support portions 9 and 11 from these two locations from the peripheral thick-walled portion 7, the The thin support part involved in detecting the electric signal is displaced and widened compared to the conventional one. Therefore, the parts on which inertial force acts, that is, the central thick part 5 and the middle thick part 6,
Even if it is considerably smaller than the conventional central thick part 20, it can be detected with better sensitivity than the conventional one.

Also, in the X direction, even if the central thick portion is considerably smaller than the conventional one, it can be detected with better sensitivity than the conventional one.

In this way, the semiconductor acceleration sensor according to this embodiment can be made smaller and have better sensitivity than the conventional one. Furthermore, since the two gaps 12 and 13 can be formed by anisotropic etching such as electric field etching as in the conventional method, it can be produced in the same process as the conventional manufacturing process.
Highly mass-producible.

[Effects of the Invention] As described above, according to the semiconductor acceleration sensor according to the present invention, it is possible to reduce the size and increase the sensitivity of the semiconductor acceleration sensor that detects three-dimensional acceleration.

[Brief explanation of drawings]

FIG. 1) is a top view of a semiconductor acceleration sensor according to an embodiment of the present invention, a sectional view taken along line A-A in FIG. 1 (θ is in FIG. 1),
Fig. 2 is an x-z cross-sectional view for explaining the X direction component, and Fig. 3 is an x-z cross-sectional view for explaining the base component in the two directions.
The cross-sectional view and Figure 4 are y for explaining the base in two directions.
-z sectional view, FIG. 5 is a diagram showing a conventional example. 1 to 4...Strain gauge group 5...Central thick part 6...Intermediate thick part 7...Peripheral thick part 8.10...Thin support part (first) 9.11. ...Thin support part (2nd) Agent: Hidekazu Miyoshi, patent attorney Figure 5

Claims (1)

[Claims] a thick-walled central thick-walled portion; a thick-walled intermediate thick-walled portion formed to surround the central thick-walled portion at a predetermined interval from the central thick-walled portion; A thick peripheral thick wall part is formed to surround the middle thick wall part with an interval of . A thin first thin support part that supports the central thick part, and at least two places on the same line that is perpendicular to a straight line connecting the two first thin support parts on the same line. a second thin-walled support portion that connects to the peripheral thick-walled portion and supports the intermediate thick-walled portion;
and a strain gauge formed above the second thin support part.