High-<i>k</i> titanium silicate thin films grown by reactive magnetron sputtering for complementary metal–oxide–semiconductor applications

Abstract

Titanium silicate (TiSixOy) thin films have been successfully deposited by means of radio-frequency magnetron sputtering of a TiO2/SiO2 composite target in a reactive gas atmosphere. The deposition of the films was investigated as a function of the [O2]/([Ar]+[O2]) flow ratio in the 0%–30% range. The bonding states and the dielectric properties of the sputter-deposited TiSixOy films were systematically investigated as a function of the O2 flow ratio. For all the O2 flow ratios studied, Fourier-transform infrared and x-ray photoelectron spectroscopy analyses have clearly revealed the presence of Ti–O–Si type of local environments, which are the fingerprint of the titanium silicate phase. Increasing the O2 proportion in the sputtering chamber was found to cause a significant decrease of the deposition rate and a drastic improvement in the dielectric properties of the films. TiSixOy films exhibiting excellent dielectric properties (i.e., a dielectric constant as high as ∼20, a dissipation factor as low as 0.01, and a low leakage current density of 10−3 A/cm2 at 1 MV/cm) were indeed achieved under high O2 flow ratio conditions (⩾20%). In contrast, films deposited under low O2 flow ratio conditions (⩽5%) have exhibited poor dielectric properties. The presence of oxygen vacancies in the films is invoked as a possible explanation for the observed variations of their dielectric properties with the O2 flow ratio.