A latch-up immune robust SCR with an N+ top.layer and an additional Nwell region (Nwell2) is proposed in this.paper. The N+ top layer and Nwell2 divide the original SCR into.three new SCRs with sharing emitter, which provide the deeper.ESD current (IESD) path to improve the holding voltage (Vh) and.failure current (It2). The relation between Vh and baseconcentration (NB) for LVTSCR is given to provide an in-depth.insight into the mechanism for enhancing Vh by changing NB..The N+ top layer and NW
