Impact of ion energies in Ar/H2 capacitively coupled radio frequency discharges on PEALD processes of titanium films

• Published in: Surface & coatings technology 2018-09, Vol.350, p.740-744
• Main Authors: Iwashita, Shinya, Denpoh, Kazuki, Kikuchi, Takamichi, Suzuki, Yusuke, Wagatsuma, Yuichiro, Hasegawa, Toshio, Moriya, Tsuyoshi
• Format: Article
• Language: English
• Subjects: Capacitively coupled discharge; Ion energy; PEALD; Titanium metal
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2018.02.068

A plasma enhanced atomic layer deposition (PEALD) process combined with ion energy control of capacitively couples radio frequency (CCRF) discharges in Ar/H2 gas mixture for fabricating Ti films was performed, and the impact of the ion energies on the film characteristics was evaluated. Titanium tetrachloride (TiCl4) was adsorbed on a silicon wafer and Ti films were synthesized via the reduction of Cl atoms from TiCl4 via the CCRF discharges. The growth per cycle of the films clearly increases with increasing the mean ion energy, ⟨εi⟩, suggesting that increase in the ion energies of the discharges promotes the reduction process of Cl atoms. Also, the film stress shows a clear dependence on ⟨εi⟩; it changes towards compressive with increasing ⟨εi⟩. On the other hand, the resistivity and the film density are almost constant independent of ⟨εi⟩, which indicates that the reduction reaction is saturated through the sequential PEALD cycles independent of ⟨εi⟩. In this paper, a simulation model based on one-dimensional (1D) Particle-in-Cell/Monte Carlo Collision (PIC/MCC) has been utilized for CCRF discharges in Ar/H2 gas mixture. •Growth per cycle and stress of Ti films clearly change depending on the ion energy.•The corresponding resistivity and film density are constant independent of the ion energy.•The difference in these film characteristics is explained by the sequential deposition process of PEALD.•Dominant reactive species in the discharges are H3+ ions according to a 1D-PIC/MCC simulation.•Hx+ and H radicals greatly contribute to the variation in the characteristics of Ti films.