Effect of Drift-Region Concentration on Hot-Carrier-Induced $R_{\rm on}$ Degradation in nLDMOS Transistors

In this letter, hot-carrier-induced on-resistance (R_on) degradation in lateral DMOS transistors with different n-type drift-drain (NDD) region concentration is investigated. Increasing NDD concentration results in greater bulk (I_b) and gate currents (I_g), but R_on degradation is improved. Technology computer-aided design simulations reveal that high NDD concentration increases impact-ionization rate in accumulation (related to I_b increase) and channel regions (related to I_g increase) but reduces impact-ionization rate in spacer region. Charge-pumping data confirm that hot-carrier-induced interface state created in the spacer region is reduced, leading to improved R_on degradation in high-NDD-concentration device.