A novel crosstalk isolation structure for bulk CMOS power IC's

This paper reports a simple and effective crosstalk isolation structure for use in bulk CMOS power integrated circuits (PIC's). Excellent crosstalk isolation characteristics were obtained by incorporating this novel crosstalk isolation structure into a CMOS/LDMOS/LIGBT high-voltage technology. The structure consists of an isolator and a collector, and is placed in the epitaxial layer between the power device and the CMOS structure. Two-dimensional (2-D) simulations were used to study the effects of the isolation structure on the carrier flow and latching mechanism in the power device/CMOS composite structure. Experimental results show that, when using the isolation structure, operating current of the body diode of the LDMOST can be improved by 16 times and operating current of the LIGBT ran be improved by five times before CMOS latchup in the control circuit occurs. The structure is also applicable for isolation between integrated conductivity modulated power devices. Over eight times reduction in current surge in the adjacent LIGBT during turn-off transient of the main LIGBT is observed.