Dielectric Constant Behavior of Hf–O–N System

Abstract

The influence of nitrogen incorporation into HfO2 has been investigated in terms of film dielectric constant and film microstructure. Static dielectric constant did not increase linearly with an increase in nitrogen concentration ([N]=N/(Hf+O+N)), but plateaued from [N] values of approximately 9 to 22 at. %. The nonlinear behavior at [N]<18 at. % was well described by the Clausius–Mossotti equation using Shannon's model of the additivity rule of static polarizabilities. Hf–N binding energy from X-ray photoelectron spectroscopy (XPS), band gap energy from reflection electron energy loss spectroscopy (REELS), conduction band offset from REELS and XPS, and refractive index from ellipsometry showed marked differences between the case of [N] values greater and less than 18 at. %. We estimated figure of merits (F.O.M.) for various high-k gate dielectrics in terms of tunneling current suppression, and found that the Hf–O–N system in the [N] range of 7.6 to 16.1 at. % showed the highest F.O.M. among the region studied.