Schottky-Embedded Isolation Ring to Improve Latch-Up Immunity Between HV and LV Circuits in a 0.18 μm BCD Technology

As the high-voltage (HV) and low-voltage (LV) circuits are integrated together in a common silicon substrate, the parasitic latch-up path between neighboring HV and LV circuits with limited spacing in layout would be triggered into latch-up state to cause unrecoverable failure in the chip. In this work, the isolation ring of HV n-well (HVNW) / N-buried layer (NBL) with Schottky-embedded junction to overcome the lateral HV-to-LV latch-up path was proposed and verified in a $0.18{\mu }\text{m}$ HV bipolar-CMOS-DMOS (BCD) technology. From the experiment results of the proposed Schottky-embedded isolation ring, the holding voltage (Vh) in the lateral HV-to-LV parasitic latch-up path can be increased to be greater than the voltage difference between the different power supplies of the neighboring HV and LV circuits. Furthermore, the layout spacing between the neighboring HV and LV circuits can be significantly reduced to save chip area. The proposed Schottky-embedded isolation ring is a cost-effective solution to provide good latch-up immunity among the HV-to-LV circuit blocks with a short layout distance.