CMOS-integrated four-contact sensors for magnetic and mechanical signals: Novel devices, systems, and applications

Semiconductor devices equipped with four contacts for measuring magnetic and mechanical signals, e.g. Hall sensors and piezoresistive stress sensing elements, have traditionally exploited the action of the external signal on currents flowing in the plane of the semiconductor chips. When operated as temperature-compensated microsensors, they are sensitive to only a small fraction of the externally applied magnetic or mechanical signal components: these are essentially the out-of-plane component of the 3D magnetic field and two in-plane stress components of the 6D stress tensor. A logical way to expand the reach of microsensors based on charge charrier transport to the entirety of applicable magneto-mechanical signals is to engineer them to include vertical current components. In addition to vertical Hall sensors for in-plane magnetic field components, stress sensors are now available for the measurement of out-of-plane normal and shear stress components. Appropriately designed, these devices can be implemented in commercial CMOS technology and thus combined with analog and digital integrated circuitry into multisensor microsystems. The art of engineering them consists of maximizing their sensitivities, while minimizing undesired effects such as offsets and cross-sensitivities, and staying within the technological constraints imposed by the CMOS technology. Applications of these novel devices range from consumer electronics and orthodontics via the automotive sector and automation to the monitoring of advanced microelectronic packaging technologies.