A novel multi-axis pendulum sandwich structure accelerometer

Abstract

This paper proposes a new scheme of pendulum accelerometer with sandwich structure. In this scheme, the electrical signal on the mass is connected to the wafer surface through glass isolated Through-Silicon-Via (TSV), so that the basic characteristics of the accelerometer can be obtained by wafer-level testing. Compared with the current commercial device process scheme, the packaging and testing cost of the device can be greatly reduced. The Glass-in-Silicon (GIS) encapsulation caps on both sides of the device are prepared by glass isolated TSV and GIS reflow process. By designing the shape and size of the silicon electrode area and glass area of the GIS caps, the parasitic capacitance between the pendulum structure and the fixed electrode is reduced. Another advantage of using TSV to extract the electrical signal of the mass is that the Z-axis inertial force can be detected when the pendulum structure is placed perpendicular to the direction of gravity acceleration. In addition, electrodes are grown on the side of the split device, and when the pendulum structure is placed parallel to the direction of gravity acceleration, the inertial force of the XY-axis can be detected. The test shows that when the range of the pendulum accelerometer based on this scheme is ±2 g, the noise density of the accelerometer is 42 μg/√Hz (X-axis), 40 μg/√Hz (Y-axis) and 27 μg/√Hz (Z-axis), and the Bias instability (BI) is 6.6 μg (X-axis), 7.1 μg (Y-axis) and 6.8 μg (Z-axis), reaching the level of commercial devices.