CMOS-integrated silicon 3d force sensor system for micro component coordinate measurement machines

This paper reports a CMOS-integrated three-axial force sensor system realized using a post-CMOS compatible low-temperature fabrication process which allows to process single IC dies as obtained from multi-project wafer (MPW) runs. The sensor system can be applied in coordinate measurement machines used for three-dimensional metrology of microcomponents. It is based on a flexible micromechanical cross structure suspended through thin silicon membrane hinges in a silicon frame. The cross is realized using double-sided deep reactive ion etching of IC chips comprising field effect transistor based piezoresistive stress sensor elements integrated with on-chip circuitry. The sensor elements are located on the membrane hinges and detect the deformations of the cross structure upon forces applied to a tactile element. The sensor system is able to monitor out-of-plane deflections of the cross structure with a resolution of 33 nm.