Determination of electron effective mass and electron affinity in HfO₂ using MOS and MOSFET structures

We present a combined electrical and modeling study to determine the tunneling electron effective mass and electron affinity for HfO₂. Experimental capacitance-voltage (C-V) and current-voltage (J-V) characteristics are presented for HfO₂ films deposited on Si(1 0 0) substrates by atomic layer deposition (ALD) and by electron beam evaporation (e-beam), with equivalent oxide thicknesses in the range 10-12.5 Å. We extend on previous studies by applying a self-consistent 1D-Schrödinger-Poisson solver to the entire gate stack, including the inter-layer SiO_x region - and to the adjacent substrate for non-local barrier tunnelling - self-consistently linked to the quantum-drift-diffusion transport model. Reverse modeling is applied to the correlated gate and drain currents in long-channel MOSFET structures. Values of (0.11 ± 0.03)m₀ and (2.0 ± 0.25) eV are determined for the HfO₂ electron effective mass and the HfO₂ electron affinity, respectively. We apply our extracted electron effective mass and electron affinity to predict leakage current densities in future 32 nm and 22 nm technology node MOSFETs with SiO_x thicknesses of 7-8 Å and HfO₂ thicknesses of 23-24 Å.