Electrical properties of MOS capacitors formed by PEALD grown Al₂O₃ on silicon

Abstract

In the present work, we have grown 2.83 nm thin Al₂O₃ films directly on pre-cleaned p-Si (100) substrate using precursor Trimethyl Aluminium (TMA) with substrate temperature of 300°C in a Plasma Enhanced Atomic Layer Deposition (PEALD) chamber. The MOS capacitors were fabricated by depositing Pt/Ti metal bilayer through shadow mask on Al₂O₃ high-k by electron beam evaporation system. The MOS devices were characterized to evaluate the electrical properties using a capacitance voltage (CV) set-up. The dielectric constant calculated through the CV analysis is 8.32 for Al₂O₃ resulting in the equivalent oxide thickness (EOT) of 1.32 nm. The flat-band shift of 0.3 V is observed in the CV curve. This slight positive shift in flat-band voltage is due to the presence of some negative trap charges in Pt/Ti/ALD-Al₂O₃/p-Si MOS capacitor. The low leakage current density of 3.08 × 10⁻¹⁰ A/cm² is observed in the JV curve at 1 V. The Si/Al₂O₃ barrier height Φ _B and the value of J _FN are calculated to be 2.78 eV and 3.4 × 10⁻⁵ A/cm² respectively.