CMOS-integrated three-axis force sensor for coordinate measurement applications

This paper reports on the development and characterization of a CMOS-integrated three-dimensional force sensor for coordinate measurement applications. In contrast to previously presented tactile sensors using the same principle of operation, this sensor features 32 PMOS piezoresistive field effect transistors as stress sensing elements. We performed calibration measurements in the x, y, and z directions and found the accuracy of this system comprising the CMOS sensor chip and a tactile metal pin to be better than ±50 nm. The ratio of stiffness against vertical and horizontal deflection of the probing system was found to be Sz/S_xy ≈ 4.8.