Spectroscopic ellipsometry time study of low-temperature plasma-polymerized plain trimethylsilane thin films deposited on silicon

In this paper, we investigate the ageing process and composition of plain trimethylsilane (TMS) plasma-polymerized films using a rotating polarizer and analyzer spectroscopic ellipsometer. Moreover, x-ray photoelectron spectroscopy (XPS) depth profiling studies on these films will be presented for a more detailed understanding of the ageing process as well as the modeling of these films. An ellipsometric study of the refractive index of these films shows that the index undergoes a substantial change with time especially in fresh films. Moreover, XPS depth profiling measurements done on these films reveal that the chemical atomic ratios of the constituents change with time. In particular, the strength of the total oxygen signal shows an increase while the strength of the total carbon signal shows a decrease with time.