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

Abstract

The density of interface states <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">it</sub> in metal-gate/high- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> 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 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">it</sub> , and a high channel resistance, i.e., the latter exacerbated by poor effective mobility, are demonstrated in capacitance-voltage ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CV</i> ) 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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.