Electrical properties of MOS capacitors formed by PEALD grown Al$_2$O$_3$ on silicon

In the present work, we have grown 2.83 nm thin Al$_2$O$_3$ films directly on pre-cleaned $p$-Si(100) substrate using precursor Trimethyl Aluminium (TMA) with substrate temperature of 300$^\circ$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 Al$_2$O$_3$ 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 Al$_2$O$_3$ resulting in the equivalent oxide thickness (EOT) of 1.33 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–Al$_2$O$_3$/$p$-Si MOS capacitor. The low leakage current density of 3.08 $\cdot$ 10$^{-10}$ A/cm$^2$ is observed in the $JV$ curve at 1 V. The Si/Al$_2$O$_3$ barrier height $\Phi_B$ and the value of $J_{\mathrm{FN}}$ are calculated to be 2.78 eV and 3.4 $\cdot$ 10$^{-5}$ A/cm$^2$ respectively.