Investigation and Suppression of Holding Voltage Deterioration in Multifinger SCR for Robust High-Voltage ESD Engineering

Abstract

For robust high-voltage (HV) electrostatic discharge (ESD) protection engineering, such as 8-KV or 15-KV ESD target, the silicon-controlled rectifiers (SCRs) with high holding voltage are needed to mitigate latch-up risk. However, when implemented in the multifinger layout configuration for satisfying high robust ESD requirement, these devices may encounter holding voltage deterioration problems. In this article, such holding voltage deterioration has been explored by theoretical analysis and experimental verification. The transmission line pulsing (TLP) results indicate that the sharing of adjacent WELL pickup and removing of inner guard ring in the typical multifinger layout (TMF) are the root causes for holding voltage deterioration. Through the appropriate test-key design, both of these culprits have been identified independently. Finally, by keeping the average WELL pickup length and average number of parasitic paths of each SCR finger in the multifinger layout constant, such holding voltage deterioration can be restrained effectively, achieving a stable holding voltage regardless of the number of fingers. Therefore, this article offers very useful work for HV ESD engineering.