Three-axes monolithic silicon low-g accelerometer

In this paper, four different designs for a new three-axes monolithic low-g acceleration sensor are presented. The silicon spring-mass system of the sensor is fabricated in a single step by anisotropic wet chemical etching in KOH using (111) planes as physical etch stop. The orientation of the supporting beams of the spring-mass systems allows the seismic mass to move in a direction orthogonal to the (111) planes. Four mass-spring systems, each one rotated by 90 degrees, enables the detection of three components of the acceleration vector using capacitive readout. Two alignment structures are presented meeting the high requirements in terms of mask alignment, which are necessary when using the described etch technique. A new space saving compensation structure protecting the convex edges of the seismic masses during the etch process was realized and compared with standard solutions. The sensors performance was characterized and is demonstrated.