A generalized EKV charge-based MOSFET model including oxide and interface traps. (March 2021) - Zhang, Chun-Min
Highlights: This work presents a generalized EKV charge-based MOSFET model that includes the effects of trapped charges in the oxide bulk and at the silicon/oxide interface- and can be applied for modeling effects of total ionizing dose, bias-temperature instability, and hot-carrier injection. In the presence of oxide- and interface-trapped charges, the mobile charge density at a given gate-to-bulk voltage can still be linearized but with respect to both the surface potential and the channel voltage, which enables us to derive explicit expressions for the charge-voltage relation, the current-charge relation, and crucial device parameters. The proposed charge-based analytical model, including the effect of velocity saturation, is successfully validated against a 28-nm bulk CMOS technology with pre-radiation and radiation measurements of various MOSFETs up to 1 Grad(SiO2 ) of total ionizing dose. Despite a small number of parameters, the model accurately captures the effects of radiation-induced oxide- and interface-trapped charges, resulting in an excellent fit with measurement results over a wide range of device operation from weak to strong inversion. Explicit expressions of device parameters allow for the extraction of the oxide- and interface-trapped charge densities at each radiation step, which can serve for compact modeling of total ionizing radiation effects. Abstract: This paper presents a generalized EKV charge-based MOSFET model that includes the effects of trapped charges in the oxide bulk and at the silicon/oxide interface. It is shown that in the presence of oxide- and interface-trapped charges, the mobile charge density can still be linearized but with respect to both the surface potential and the channel voltage. This enables us to derive closed-form expressions for the mobile charge density and the drain current. These simple formulations demonstrate the effects of charge trapping on MOSFET characteristics and crucial device parameters. The proposed charge-based analytical model, including the effect of velocity saturation, is successfully validated through measurements performed on devices from a 28-nm bulk CMOS technology. Ultrahigh total ionizing doses up to 1 Grad(SiO2 ) are applied to generate oxide-trapped charges and activate passivated interface traps. Despite a small number of parameters, the model is capable of accurately capturing measurement results over a wide range of device operation from weak to strong inversion. Explicit expressions of device parameters also allow for the extraction of the oxide- and interface-trapped charge densities.