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

The density of interface states
D
_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
_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 HfO
₂
/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.