Sensitivity tuning of A 3-axial piezoresistive force sensor

Design and development of a Si based full membrane piezoresistive 3D force sensor is presented in this paper. Four piezoresistors are formed by ion implantation on the back side of a thin Si membrane, while on the front side a 380 μm high Si mesa is produced by subtractive dry etching (deep reactive ion etching). The external force is applied on the top of the mesa. The applied force vector, i.e. its normal and shear force components are determined by combining the responses of the four piezoresistors. The effect of different parameters - the shape and thickness of the membrane, the cross section of the mesa - on the sensitivity of the sensor is analyzed systematically by finite element methods. Comparison of the characteristics of the different sensor designs obtained from simulations and from experimental measurements is also presented.