摘要
This work investigates the impact of isolated-ring (ISO-ring) connection schemes on the second breakdown current (It2) of a fully isolated laterally diffused NMOSFET (ISO-LDNMOS). The device exhibits significantly enhanced ESD robustness when the N-ISO is tied to the drain and the P-ISO is grounded, compared with configurations in which both ISO-rings are grounded or floating. TCAD simulations show that floating or grounding both ISO-rings triggers snapback the base push-out (Kirk) effect, leading to premature failure. In contrast, connecting the N-ISO to the drain while grounding the P-ISO suppresses the Kirk effect and substantially improves It2.