Etching characteristics and mechanisms of Mo thin films in Cl₂/Ar and CF₄/Ar inductively coupled plasmas

Abstract

The etching characteristics and mechanism of Mo thin films in Cl 2 /Ar and CF 4 /Ar inductively coupled plasmas under the same operating conditions (pressure, 6 mTorr; input power, 700 W; bias power, 200 W) were investigated. For both gas mixtures, an increase in the Ar fraction or gas pressure at a fixed gas mixing ratio was found to cause a non-monotonic change in the Mo etching rates. The X-ray photoelectron spectroscopy (XPS) diagnostics indicated contamination of the etched surfaces by reaction products. The Cl 2 /Ar and CF 4 /Ar plasma parameters were also investigated using a combination of a zero-dimensional plasma model and plasma diagnostics using Langmuir probes. An analysis of the etching kinetics with the model-predicted fluxes of the plasma active species suggests that: 1) the Mo etching process occurs in the transitional regime of the ion-assisted chemical reaction, and 2) the non-monotonic Mo etching rate is probably associated with opposing changes in the fluxes of the reactive neutral species and ion energy.

Contribution of Ion Energy and Flux on High-Aspect Ratio SiO2 Etching Characteristics in a Dual-Frequency Capacitively Coupled Ar/C4F8 Plasma: Individual Ion Energy and Flux Controlled

“…Several studies used optical emission spectroscopy [ 27 , 28 ] and a quadrupole mass spectrometer [ 2 , 29 ] for estimating radicals densities, but its accuracy remains questionable. Alternatively, a volume-averaged model was used for analyzing plasma chemistry in a complex gas mixture [ 30 , 31 , 32 ]. We developed an in-house volume-averaged model code for C F /Ar plasma.…”