A Novel ‘I-V Spectroscopy’ Technique to Deconvolve Threshold Voltage and Mobility Degradation in LDMOS Transistors

Abstract

Although the CMOS-compatible Laterally Diffused MOSFET (LDMOS) is widely used in various applications as a versatile and efficient power electronic device, its hot carrier degradation (HCD) remains a persistent and important design challenge. None of the classical HCD models apply, because the geometric and doping complexities of the channel and drift regions create multiple hotspots with bias-dependent hot carrier injection into the oxide. To address these challenges, here we: 1) propose a novel geometrical partition of the LDMOS and represent each part by a TCAD-calibrated and experimentally validated tandem-FET compact model; 2) use the new compact model to propose an ‘ I − V spectroscopy’ methodology to deconvolve mobility and threshold degradation in the channel and the drift regions; 3) separate the degradation in the two regions by postprocessing measured I-V curves; 4) demonstrate that ΔVth determined by classical techniques, e.g., constant current (CC) or maximum transconductance (Gmmax), are contaminated by mobility degradation and must be corrected by the proposed technique for accurate lifetime projection.