Multi-axis capacitive accelerometer

Abstract

A multi-axis capacitive accelerometer is consisted of a substrate with sensing electrodes and a structure layer. The structure layer includes anchor bases fixed on the substrate, a movable first proof mass, a group of first flexible structures, a plurality of fixed sensing blocks, a second proof mass, a third proof mass, a second flexible structure and a third flexible structure. The first proof mass is disposed over the substrate and has a first opening and a second opening symmetric to each other. The flexible structures are connected with the anchor bases and the first proof mass. The fixed sensing blocks are disposed on the substrate, and capacitors are formed between each fixed sensing block and the first proof mass for sensing acceleration along two in-plane directions. The second proof mass and the third proof mass are disposed over the substrate and in the first opening and the second opening and are asymmetrically suspended over the first proof mass respectively by the second flexible structure and the third flexible structure. Separate electrodes are disposed on the substrate and form two differential capacitors with the second proof mass and the third proof mass for sensing the out-of-plane acceleration.

Description

technical field [0001] The present invention relates to a capacitive accelerometer, and in particular to the design of a multi-axis capacitive accelerometer. Background technique [0002] Accelerometers are currently widely used in many devices in the market as motion sensors, such as game consoles, health monitoring, mobile phone interface control and automatic mute, inertial cursor pointers and other fields. [0003] Traditional micro-electromechanical three-axis accelerometers mostly adopt a single-axis combined three-axis design, which means that the masses and sensing elements used to sense the acceleration of the X-axis, Y-axis, and Z-axis are set independently. Although this arrangement can achieve the purpose of reducing the sensitivity of its axis in acceleration sensing, its disadvantage is that in order to achieve the goal of low mechanical noise, the size of the component is often too large, or in order to achieve the goal of small size, the mechanical noise The...

AI Technical Summary

Problems solved by technology

Generally speaking, for the design of a three-axis integrated accelerometer, when the Z-axis torsion structure is designed within the XY-axis structure, because the symmetry of the XY-axis structure mass must be considered, its rotation axis will be symmetrically placed at the center of the XY-axis structure , so that the effective area utilization rate of the lighter side of the mass block is reduced; in addition, when the Z-axis torsion structure is designed within the XY-axis structure, if the manufacturing method is to use two electrodes on another substrate to form a differential capacitance with the structure , although the Z-axis capacitance of this design is very low affected by its axial force, but in order to achieve mass symmetry, it will also cause it to use a part of the area only for mass balance and cannot contribute to sensing purposes, and The design using two sets of torsion structures can naturally form symmetry without forcing the rotation axis to be placed at the center of the XY axis structural mass, which can achieve the purpose of improving the area utilization efficiency and reducing the other axis sensitivity of the Z axis

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