High holding voltage SCR for robust electrostatic discharge protection

摘要

A novel silicon controlled rectifier (SCR) with high holding voltage (Vh) for electrostatic discharge (ESD) protection is proposed and investigated in this paper.The proposed SCR obtains high Vh by adding a long N+ layer (LN+) and a long P+ layer (LP+),which divide the conventional low voltage trigger silicon controlled rectifier (LVTSCR) into two SCRs (SCRI:P+/Nwell/Pwell/N+ and SCR2:P+/LN+/LP+/N+) with a shared emitter.Under the low ESD current (IESD),the two SCRs are turned on at the same time to induce the first snapback with high Vh (Vh1).As the IESD increases,the SCR2 will be turned off because of its low current gain.Therefore,the IESD will flow through the longer SCR1 path,bypassing SCR2,which induces the second snapback with high Vh (Vh2).The anti-latch-up ability of the proposed SCR for ESD protection is proved by a dynamic TLP-like (Transmission Line Pulse-like) simulation.An optimized Vh2 of 7.4 V with a maximum failure current (It2) of 14.7 mA/μm is obtained by the simulation.