Active field canceling system in next generation nano-Fab

Abstract

The extremely low frequency (ELF) magnetic fields from power-line current influences the yield of CMOS foundry. The poor yield happens because of ELF magnetic fields inducing directly the measurement or process equipment for cutting-edge chips below 28 nm process. The equipment of Electron microscopes, included SEM, TEM, STEM, FIB writers and E-Beam Writers are very susceptible to ELF magnetic fields emanating from various electrical power sources outside of the building and within next generation CMOS foundry recommends a maximum of 0.3 mG. There are three methods to reduce EMI, including active canceling system, passive shielding and hybrid canceling technology. The disadvantages of passive shielding is that needs expensive material shielding build anti-magnetic chamber protecting sensitive equipment with high-mu materials which is the standard method in most cases of shielding. Furthermore, active system is more flexible than passive method. The active canceling method uses active coils with current sensing field via sensor and inducing man-made electromagnetic field to reduce the stray magnetic field. Unfortunately, the conventional system takes more time to products field because of parasitical capacitance and resistance in long coil. The longer canceling coil we construct, the more time it takes. Besides, We should spend more time on calibrating non-linear current amplifier through software design. This research designs simpler anti-electro-magnetic system instead of typical frame and develops one turn canceling coil structure to reduce delaying time. Several parallel cells generates field up to 23.81 mG controlled by MCU. This system decreases the power-line inducing filed below 0.3mG.