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 SiOx 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 SiOx thicknesses of 7–8 Å and HfO2 thicknesses of 23–24 Å.