Drain Side Area-Modulation Effect of Parasitic Schottky Diode on ESD Reliability for High Voltage P-Channel Lateral-Diffused MOSFETs

Abstract

This letter focused on the additive effect of horizontal Schottky diodes on the drain side of a high-voltage p-channel laterally diffused metal–oxide–semiconductor (pLDMOS). These components were evaluated using transmission-line pulse and human body model (HBM) tests. When the parasitic Schottky area at the drain was smaller, the Schottky characteristics were less obvious; the device’s current mostly flowed through the heavily doped $\text{P}^{+}$ area, and the improvement in ${I}_{\text {t2}}$ was minor. When the parasitic Schottky area covered more than 60% of the drain side, the Schottky area accounted for the majority of current flow; therefore, the electrostatic discharge current could flow more evenly. These modified pLDMOSs can withstand higher voltages because of their parasitic Schottky diodes and higher impedance. In addition, their ${I}_{\text {t2}}$ values are superior to those of normal pLDMOSs. With the drain side of the pLDMOS completely covered by Schottky diodes, the device produced the highest ${I}_{\text {t2}}$ value of 1.659 A (130.4% higher than that of the reference sample), an HBM value of 5 kV (300% higher than the reference), and an improved holding voltage (4% greater than that of the reference).