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

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.