Silicon integrated accelerometer

• US 6,683,358 B1
• Filed: 05/10/2000
• Issued: 01/27/2004
• Est. Priority Date: 11/11/1997
• Status: Expired due to Term

• Current Assignee: Asahi Kasei Kabushiki Kaisha, Makoto Ishida
• Original Assignee: Asahi Kasei Kabushiki Kaisha
• Inventors: Matsumoto, Yoshinori, Ishida, Makoto, Takao, Hidekuni
• Primary Examiner(s): Eckert, George
• Assistant Examiner(s): RICHARDS, NORMAN DREW
• Application Number:
  US09/554,241
• Time in Patent Office: 1,357 Days
• Field of Search: 257/254, 257/415, 257/417, 257/419, 257/420, 257/414
• US Class Current: 257/417
• CPC Class Codes: B81B 3/0018 Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
• CPC Class Codes: G01P 15/0802 Details
• 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

In an accelerometer, the stress is detected through electric amplification with the use of detecting elements 411-434 having an amplification function arranged on beams 3 and, with the use of a differential amplifier circuits 510 formed on the support base 1, an acceleration component in a detection axis direction to which the stress is applied is outputted as the differential mode and acceleration components in the other axis directions are outputted as the common mode, so that each axis sensitivity ratio between the detection axis sensitivity and the other axis sensitivities is enhanced largely.

Claims

1. A silicon integrated accelerometer comprising a fixed support base, a movable seismic mass, and beams having a thin thickness connecting said support base and said seismic mass, capable of measuring acceleration by detecting mechanical stresses based on bending of said beams, said accelerometer comprising:

a plurality of strain detecting elements arranged on said beams, composed of MOS (metal oxide semiconductor) transistors, for detecting said mechanical stresses; and

a differential amplifier circuit, provided with a differential amplifying function, said circuit producing an output signal proportional to a differential signal due to said mechanical stresses obtained from a pair of said strain detecting elements;

wherein said MOS transistors according to said pair of strain detecting elements are structured as a part of a source coupling circuit,

wherein said pair of strain detecting elements is operated in saturation region so that said output signal is amplified when said pair of strain detecting elements detect said mechanical stresses as a differential mode according to a home axis direction component to which the stress is applied and so that said output signal is reduced to zero when said pair of strain detecting elements detect said mechanical stresses as a common mode according to other axis direction components to which the stress is applied.

2. A silicon integrated accelerometer as claimed in claim 1, wherein stress concentration portions of said beams are a boundary portion on said beams connected to at least one of said support base and said seismic mass.

3. A silicon integrated accelerometer as claimed in claim 2, wherein said strain detecting elements are located at said stress concentration portions.

4. A silicon integrated accelerometer as claimed in claim 1, wherein said support base and said seismic mass, and said beams are structured by using (100)-oriented silicon single crystal substrate and said beams are arranged in a direction parallel to the crystallographic axis <

011>

.

5. A silicon integrated accelerometer as claimed in claim 1, wherein said seismic mass surrounds said support base.

6. A silicon integrated accelerometer as claimed in claim 1, wherein

at least one of said beams is arranged at each of both sides of either said support base or said seismic mass, and

said differential amplifier circuit is structured by arranging two strain detecting elements at the boundary portions between each said beam and said support base.

7. A silicon integrated accelerometer as claimed in claim 1, wherein

at least one of said beams is arranged at each of both sides of either said support base or said seismic mass, and

said differential amplifier circuit is structured by arranging two strain detecting elements at the boundary portions between each said beam and said seismic mass.

8. A silicon integrated accelerometer as claimed in claim 1, wherein

at least one of said beams is arranged at each of both sides of either said support base or said seismic mass, and

said differential amplifier circuit is structured by arranging one strain detecting element at the boundary portion between each said beam and said support base and by arranging one strain detecting element at the boundary portion between each said beam and said seismic mass.

9. A silicon integrated accelerometer as claimed in claim 1, further comprising:

two current sources for driving two pairs of the differential amplifier circuits detecting an acceleration component in a uni-axial direction, and

a switch for switching of said two current sources at high frequency.