$D_{rm it}$ Extraction From Conductance-Frequency Measurements using a Transmission-Line Model in Weak Inversion of $hbox{poly/TiN/HfO}_{2}$ nMOSFETs

摘要

The density of interface states $D_{rm it}$ in metal-gate/high-$k$ dielectric MOSFETs is investigated in weak inversion from small-signal capacitance and conductance measurements using a transmission-line model. A presence of both, a large $D_{rm it}$, and a high channel resistance, i.e., the latter exacerbated by poor effective mobility, are demonstrated in capacitance–voltage ( $CV$) characteristics by a comparison of experiments with simulations using a Schrodinger–Poisson solver. Using a transmission-line network, the channel response and the density of interface states can be accurately modeled from the conductance-frequency characteristics. This technique is applied to $hbox{HfO}_{2}hbox{/SiO}_{2}$ dielectric MOSFETs with polysilicon and poly/TiN metal gates deposited and annealed at identical temperature. In such a condition, the density of interface states is twice as large as for a TiN metal gate.