Three-axis accelerometers and fabrication methods

Abstract

Disclosed are MEMS accelerometers and methods for fabricating same. An exemplary accelerometer comprises a substrate, and a proof mass that is a portion of the substrate and which is separated from the substrate surrounding it by a gap. An electrically-conductive anchor is coupled to the proof mass, and a plurality of electrically-conductive suspension anus that are separated from the proof mass extend from the anchor and are coupled to the substrate surrounding the proof mass. A plurality of sense and actuation electrodes are separated from the proof mass by gaps and are coupled to processing electronics. Capacitive sensing is used to derive electrical signals caused by forces exerted on the proof mass, and the electrical signals are processed by the processing electronics to produce x-, y- and z-direction acceleration data. Electrostatic actuation is used to induce movements of the mass for force balance operation, or self-test and self-calibration. The fabrication methods use deep reactive ion etch bulk micromachining and surface micromachining to form the proof mass, suspension arms and electrodes. The anchor, suspension arms and electrodes are made in the same process steps from the same electrically conductive material, which is different from the substrate material.