An inductive MEMS accelerometer

In this paper, a linear single axis electromagnetic accelerometer with new sensing principle has been proposed. The accelerometer consists of fixed planar spiral inductor that has been sandwiched between two ferromagnetic layers. One of the layers is under the planar coil and the other one is attached to the proof-mass of the accelerometer. The principle of the design is based on the inductance variation due to vertical distance changing between the ferromagnetic layers. The salient feature of the proposed structure is the high dependence of its sensitivity to the ferromagnetic layers thickness and relative permeability. Therefore in a fixed die size the sensitivity can be improved by controlling aforementioned parameters. The advantage of proposed method is that the sensitivity can be increased by using thicker ferromagnetic layers with higher relative permeability which is achievable in micro fabrication without altering the accelerometer layout.