Acceleration sensor with seismic mass and bending section - embedded in evacuated cavity inside layers of silicon so that movement varies capacitance

摘要

The sensor consists of three silicon layers (1,2,3) with a movable structure (4) in the middle layer (2). The movable structure (4) is formed of a bending section (30) with seismic mass (31), and positioned within a cavity (5). The external layer (3) has a hole (6) to permit evacuation of the cavity, and is subsequently closed by a layer (10). As the mass (31) moves under acceleration, the capacitance between pair of layers (1,2) and (2,3) varies. Silicon layers are isolated to allow movement. ADVANTAGE - Use of evacuated cavity for sensor moving mass reduces damping and improves response.