JPH04279867A - Three-dimensional acceleration sensor - Google Patents

Abstract

PURPOSE:To detect three-dimensional acceleration independently by arranging a plurality of one-dimensional acceleration sensors provided with anti-shock strength against acceleration which is not in the detectional direction, on one chip. CONSTITUTION:A center thick part 7 is supported by a thin part 8 opposed thereto in an inboard structure, while X- and Y-direction acceleration sensors 2, 3 provided with the sensitivity for only the vibration in the lateral direction in parallel to a chip, added to both of the thin parts, as well as a center thick part 12 are supported by a thin part 13 in am overhung structure, and a Z- direction acceleration sensor 4 provided with the sensitivity for only the vibration in the vertical direction of the chip, and these acceleration sensors are arranged on the same one chip. A diffusive strain gages R are provided in the parts of the thin parts where the stress is generated, and a bridge circuit is formed out of this strain gage. The acceleration component of each direction is detected by each sensor, and by analyzing the sensor output, the degree of acceleration in three-dimensional direction is measured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional acceleration sensor suitable for independently detecting acceleration in the X-, Y-, and Z-axis directions.

0002

2. Description of the Related Art A three-dimensional acceleration sensor is disclosed, for example, in Japanese Patent Application Laid-open No. 118260/1983. This three-dimensional acceleration sensor has three independent acceleration sensor chips arranged on a single silicon chip with sensitivity in each dimension direction. Each acceleration sensor chip has a cantilevered structure in which a central thick wall part and a peripheral thick wall part are connected by a single thin wall part, and acceleration is detected by a strain gauge provided at the stress generating site of this thin wall part. It is composed of

0003

[Problem to be Solved by the Invention] When arranging acceleration sensors in the X, Y, and Z axis directions on the same plane, using the same cantilevered structure for the acceleration sensors in each axis direction causes acceleration in directions that are not desired to be detected. It is also possible that the strain stress generated by this acceleration will affect the acceleration component in the direction that is desired to be detected. Furthermore, the cantilevered structure is disadvantageous in terms of impact resistance against acceleration in the X and Y directions parallel to the acceleration sensor chip surface. An object of the present invention is to provide a three-dimensional acceleration sensor that is capable of independently detecting three-dimensional acceleration by arranging a plurality of one-dimensional acceleration sensors on one chip that have impact resistance against acceleration that is not in the detection direction. An object of the present invention is to provide an acceleration sensor.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a through part between a peripheral thick part and a central thick part, and the thick parts are connected by a thin part. and a diffusion strain gauge is disposed in the thin wall portion where strain stress is generated due to vibration of the central thick wall portion, wherein the central thick wall portion is supported by the opposing thin wall portion in a dual support structure. The center thick part is supported by the thin part in a cantilevered structure, and the center thick part is supported by the thin part in a cantilevered structure, and Z sensitive only to vibrations
In addition to placing the directional acceleration sensor on the same chip,
A bridge circuit is configured to independently detect unidirectional acceleration using the diffusion strain gauge of each sensor.

[0005]

[Operation] Acceleration sensors that are sensitive only to vibrations in one-dimensional direction are arranged in each three-dimensional direction, so each sensor detects acceleration components in each direction, and these sensors By analyzing the output, the magnitude of acceleration in three-dimensional directions can be measured.

[0006]

[Embodiment] An embodiment of the present invention will be explained based on the drawings. FIG. 1a shows the arrangement of a sensor chip of a three-dimensional acceleration sensor. The three-dimensional acceleration sensor 1 is
A directional acceleration sensor 2, a Y-direction acceleration sensor 3, and a Z-direction acceleration sensor 4 are arranged so that acceleration in each direction can be detected independently. Note that since the X and Y direction acceleration sensors 2 and 3 have the same structure and are arranged with their sensing directions shifted by 90 degrees, only the X direction acceleration sensor 2 will be described here.

The X-direction acceleration sensor 2 includes an acceleration sensor chip manufactured using semiconductor manufacturing technology. As shown in Figure 1b, this sensor chip includes a diffusion strain gauge (hereinafter referred to as a "strain gauge") that detects stress strain caused by vibration on a silicon wafer, and wiring for connecting the strain gauge to a processing circuit such as an amplifier circuit. After forming an electrode pattern (not shown) such as a bonding pad, a through portion 5 having a U-shaped cross section is formed by anisotropic etching from both sides of the wafer. This penetrating portion 5 provides a central thick-walled portion 7 surrounded on all sides by peripheral thick-walled portions 6. It is connected to section 6. That is, the thin wall portion 8 has a<<b in the illustrated dimensions, is easily deformed in the direction of the through portion (X or Y), and has a thickness of the chip (
It has a structure that is difficult to deform in the Z) direction.

When vibration is applied in the X (or Y) direction as shown in the figure, since the central thick part 7 is supported by the thin part 8 in a dual support structure, the connection between the two thin parts 8 and the peripheral thick part 6 is interrupted. Distortion stress occurs in the part. In order to detect this strain stress,
A pair of strain gauges R are arranged in each thin wall portion 8 and arranged in the vibration sensing direction. These strain gauges R are electrically connected to form a bridge circuit. For example, in the case of a strain gauge arrangement in which strain gauges R1 and R2 are placed on one thin wall portion 8 and strain gauges R3 and R4 are placed on the other thin wall portion 8 as shown in FIG. 2c, as shown in FIG. A bridge circuit is constructed in which R1 and R3 and R2 and R4 are arranged on opposite sides. Here, the resistance change of the strain gauge increases (
(symbol “↑”), while decreasing for compressive stress (symbol “↓”)
")do. For example, when acceleration G is applied in the direction of the arrow shown in FIG. 2a, the resistance of strain gauges R2 and R4 increases due to tensile stress, and the resistance of strain gauges R1 and R3 decreases due to compressive stress. The resistance change at this time is shown in FIG. 2c.

The Z-direction acceleration sensor 4 is manufactured using the same semiconductor manufacturing technology as described above, and is provided with a central thick portion 12 surrounded by peripheral thick portions 11 on all sides by a through portion 10. 12 has a cantilevered structure connected to the peripheral thick part 11 by one thin part 13. That is, the thin-walled portion 13 has c>>d in the illustrated dimensions, and has a structure that allows it to easily deform in the vertical (Z) direction of the chip, while being difficult to deform in the through-part (X and Y) directions. It has become. Therefore, when the center thick part 7 is subjected to vibration in the Z direction shown in the figure, the thin part 13 and the peripheral thick part 11
Distortion stress occurs in the connected parts. In order to detect this strain stress, a pair of strain gauges R (R1 to R4) arranged in the vibration sensing direction and the non-vibration sensing direction are arranged in the thin portion 13 as shown in FIG. 2b. This strain gauge R constitutes a bridge circuit shown in FIG. 2c.

The operation of the three-dimensional acceleration sensor of the above embodiment will be explained. As shown in FIG. 1, the sensor chips are arranged so as to be sensitive only to vibrations in each direction, so each sensor chip detects the magnitude of the acceleration component in that direction. Therefore, by analyzing sensor outputs in three directions, the direction and magnitude of acceleration can be measured.

By the way, since the sensor sensitivity changes depending on the mass of the central thick wall portion, it is also possible to further add weight to the central thick wall portion to increase the sensor sensitivity. For example, as shown by the two-dot chain line in FIG. 1, a spherical weight 14 is fixed to the upper or lower surface of the central thick portion. As the weight 14, a solderable metal ball such as copper, a surface-treated ball, or a glass ball is used. With this configuration, the mass of the central thick part increases due to the addition of weight, so the sensor chip
When receiving acceleration in this direction, a torsional moment is generated around the center of gravity, and the acceleration in the X and Y axis directions can be detected as a composite value.

0012

Effects of the Invention As described above, according to the present invention, a plurality of sensors sensitive only to vibrations in one direction are arranged on one chip with sensitivity in multiple directions, so that the entire sensor can be made smaller and lower in cost.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a three-dimensional acceleration sensor of the present invention,
(a) is a sensor arrangement diagram, (b) is a perspective view of an X- and Y-direction acceleration sensor, and (c) is a perspective view of a Z-direction acceleration sensor.

2 is a diagram illustrating acceleration detection in each direction shown in FIG. 1, where (a) is a strain gauge arrangement diagram of X and Y direction acceleration sensors;
(b) is a strain gauge layout diagram of the Z-direction acceleration sensor, (c)
is a bridge circuit diagram composed of strain gauges in each direction.

[Explanation of symbols]

1 Sensor chip 2 X direction acceleration sensor 3 Y direction acceleration sensor 4 Z direction acceleration sensor 5,10 Penetration part 6,11 Peripheral thick wall part 7, 12 Central thick part 8,13 Thin wall part R Strain gauge

Claims (1)

[Claims] 1. A penetrating portion is provided between a peripheral thick wall portion and a central thick wall portion, the thick wall portions are connected by a thin wall portion, and strain stress is generated by vibration of the central thick wall portion. A semiconductor acceleration sensor in which a diffusion strain gauge is disposed in the thin-walled portion, wherein the central thick-walled portion is supported by the opposing thin-walled portions in a dual-support structure, and lateral vibrations parallel to the chip are applied to both the thin-walled portions. An acceleration sensor in the X and Y directions that is sensitive only to vibrations in the vertical direction, and an acceleration sensor in the Z direction that is sensitive only to vibrations in the vertical direction of the chip, the central thick part of which is supported by a thin part in a cantilevered structure, and a Z direction acceleration sensor that is sensitive only to vibrations in the vertical direction of the chip are mounted on the same chip. The three-dimensional acceleration sensor is configured with a bridge circuit that independently detects unidirectional acceleration using the diffusion strain gauge of each sensor.