Semiconductor Acceleration Sensor

• US 20080271535A1
• Filed: 03/29/2006
• Published: 11/06/2008
• Est. Priority Date: 03/30/2005
• Status: Active Grant

• Current Assignee: Yokohama Rubber Company Limited
• Original Assignee: Yokohama Rubber Company Limited
• Inventors: Hatano, Yasuo, Hattori, Yutaka
• Granted Patent: US 7,827,865 B2
• Time in Patent Office: Days
• US Class Current: 73/514.33
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass

Abstract

An object of the present invention is to provide a semiconductor acceleration sensor capable of sensing accelerations in two directions parallel to the surface of a diaphragm and orthogonal to each other with respective proper sensitivities.

There is constructed a semiconductor acceleration sensor 10 constituted of diaphragm pieces 13a to 13d extending from the center of the diaphragm surface to a wafer outer-circumferential frame section 12a, respectively, along an X axis direction and a Y axis direction orthogonal to each other. On the upper surface of the diaphragm pieces, there are formed piezo resistors Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4. In the diaphragm pieces 13a and 13b disposed on a single line along the X axis direction and the diaphragm pieces 13c and 13d disposed on a single line along the Y axis direction, the areas of cross section orthogonal to the axis are set according to a maximum value of acceleration, respectively, in the X axis direction or Y axis direction.

Claims

1. A semiconductor acceleration sensor, comprising:

a silicon wafer having a diaphragm formed within a wafer outer-circumferential frame section;

a pedestal securing the wafer outer-circumferential frame section;

a plumb bob disposed in the center of one surface of the diaphragm; and

a plurality of beams extending, respectively, from the center of the surface of the diaphragm to the wafer outer-circumferential frame section along X axis and Y axis directions parallel to the surface of the diaphragm and orthogonal to each other,

wherein the areas of cross section of the plurality of beams orthogonal to each axis at a predetermined position are set according to a maximum value of respective accelerations in the X axis and Y axis directions.

2. The semiconductor acceleration sensor according to claim 1, wherein in each of the beam disposed along the X axis direction and the beam disposed along the Y axis direction, the cross section area at two points symmetrical around the center is identical.

3. The semiconductor acceleration sensor according to claim 1, wherein in the beam disposed along the X axis direction and/or the beam disposed along the Y axis direction, the cross section area increases in a direction from the center to the wafer outer-circumferential frame section.

4. The semiconductor acceleration sensor according to claim 1, wherein to allow sensing of respective accelerations in the X axis and Y axis directions and a Z axis direction orthogonal to the surface of the diaphragm, a diffused resistor is arranged in each of the plurality of beams and at the same time, on the wafer outer-circumferential frame section corresponding to each of the plurality of beams, there is provided an connection electrode connected to the diffused resistor.

5. The semiconductor acceleration sensor according to claim 1, wherein the diaphragm is a silicon piezo diaphragm.

6. The semiconductor acceleration sensor according to claim 1, wherein in one surface side and/or the other surface side of the diaphragm, there is provided a protrusion secured to a position spaced with a predetermined gap from the surface of the center of the diaphragm and/or from the surface of the plumb bob corresponding to the center, and protruding opposite the center.

7. The semiconductor acceleration sensor according to claim 6, wherein the protrusion is secured and supported to the wafer outer-circumferential frame section and/or the pedestal and disposed at a position spaced with a predetermined gap from the center of the other surface of the diaphragm so as to protrude opposite the center of the other surface of the diaphragm.

8. The semiconductor acceleration sensor according to claim 6, wherein that the protrusion is joined and supported to the wafer outer-circumferential frame section and/or the pedestal and disposed at a position spaced with a predetermined gap from the center of the plumb bob so as to protrude opposite the surface of the plumb bob.

9. The semiconductor acceleration sensor according to claim 6, wherein the tip end of the protrusion corresponding to the surface of the center of the diaphragm and/or to the surface of the plumb bob corresponding to the center has a cone-shaped tip end configuration.