An Improved Silicon-Controlled Rectifier (SCR) for Low-Voltage ESD Application

In this article, an improved silicon-controlled rectifier (SCR) for low-voltage (LV) electrostatic discharge (ESD) applications has been presented. By employing an N+/P-ESD diode and optimizing the SCR layout, both the triggering and current-discharging paths of the new SCR become much shorter than the prior arts, thus generating better clamping ability, faster turn-on speed, and lower overshoot voltage. As a result, the human body model (HBM) robustness increases by 19%, 46%, and 267% for the proposed device with one, two, and three stacking units, respectively, and the charged-device model (CDM) robustness and turn-on speed of the improved device increase by 80% and 27%, respectively, over its conventional counterpart. Furthermore, the contradiction between quasi-static triggering characteristics and transient overshoot voltage frequent in current-assisted triggering of ESD devices has been investigated, where the common method to optimize the trigger voltage by increasing the resistance of triggering path will deteriorate the overshoot characteristics hugely. To make the ESD devices satisfy the emerging higher CDM protection requirement, a tradeoff between the quasi-static trigger voltage and the transient overshoot voltage should be made elaborately.