Design and Optimization of ESD Protection Structure Triggered by Polysilicon Diode for Low- and Medium-Voltage ICs

A novel silicon-controlled rectifier (SCR) triggered by multiple polysilicon diodes (MPDTSCR) is proposed and investigated for electrostatic discharge (ESD) protection in low- and medium-voltage integrated circuits (ICs). Typically, the turn-on voltage of a conventional diode-triggered SCR (DTSCR) does not increase linearly when more than three diodes in series, due to parasitic effects caused by the complex bipolar transistors formed by multiple p-n junctions, leading to unpredictable turn-on voltage and increased leakage current. By innovatively designing a compact polysilicon-diode triggering circuit, the MPDTSCR with six polysilicon diodes exhibits excellent anti-parasitic ability and favorable electrical characteristics, achieving a low breakdown voltage of 4.2 V, a small leakage current in the nanoampere scales, and high robustness with a failure current level of 6.6 A per finger. By minimizing the space between the p- and n-type regions of the polysilicon, the turn-on voltage of the MPDTSCR is reduced from 17.2 to 13 V, without degrading the ESD robustness. Therefore, the SCR embedded with a compact polysilicon-diode-triggering circuit effectively suppresses parasitic effects. The MPDTSCR, with its innovative design and adjustable number of polysilicon diodes, offers excellent adaptability for effective ESD protection in low- and medium-voltage applications, ensuring comprehensive protection and highlighting its significance in enhancing the reliability and stability of modern electronic systems.