MOS Capacitance Measurements for PEALD TiO Dielectric Films Grown under Different Conditions and the Impact of AlO Partial-Monolayer Insertion.

In this paper, we report the plasma-enhanced atomic layer deposition (PEALD) of TiO and TiO/AlO nanolaminate films on p-Si(100) to fabricate metal-oxide-semiconductor (MOS) capacitors. In the PEALD process, we used titanium tetraisopropoxide (TTIP) as a titanium precursor, trimethyl aluminum (TMA) as an aluminum precursor and O plasma as an oxidant, keeping the process temperature at 250 °C. The effects of PEALD process parameters, such as RF power, substrate exposure mode (direct or remote plasma exposure) and AlO partial-monolayer insertion (generating a nanolaminate structure) on the physical and chemical properties of the TiO films were investigated by Rutherford backscattering spectroscopy (RBS), Raman spectroscopy, grazing incidence X-ray diffraction (GIXRD), and field emission scanning electron microscopy (FESEM) techniques. The MOS capacitor structures were fabricated by evaporation of Al gates through mechanical mask on PEALD TiO thin film, followed by evaporation of an Al layer on the back side of the Si substrate. The capacitors were characterized by current density-voltage (J-V), capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. Our results indicate that RF power and exposure mode promoted significant modifications on the characteristics of the PEALD TiO films, while the insertion of AlO partial monolayers allows the synthesis of TiO/AlO nanolaminate with well-spaced crystalline TiO grains in an amorphous structure. The electrical characterization of the MOS structures evidenced a significant leakage current in the accumulation region in the PEALD TiO films, which could be reduced by the addition of partial-monolayers of AlO in the bulk of TiO films or by reducing RF power.