Etch Properties of TiN Thin Film in Metal--Insulator--Metal Capacitor Using Inductively Coupled Plasma

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In this work, we investigated the etching characteristics of the titanium nitride (TiN) thin film in BCl3/Cl2 plasma and the effect of the gases (O2 and Ar) added to BCl3/Cl2 plasma. The etch rate was measured under various etching conditions, such as the gas mixing ratio, the process pressure and the substrate temperature. The maximum etch rate of TiN thin film was 343 nm/min in BCl3 (25%)/Cl2 (75%) plasma. To enhance the etching characteristics, we added O2 and Ar gas to BCl3 (25%)/Cl2 (75%) plasma. Added O2 and Ar gas flow rates were 2, 5, 8, and 10 sccm. The etch rates with O2 addition decrease from 221 to 4 nm/min. The etch rate in Ar/BCl3/Cl2 plasma decreased slightly compared with that in the case of O2 addition. The nonvolatile etched byproduct was formed on the surface, and was analyzed by X-ray photoelectron spectroscopy (XPS) analysis. O2 addition without Ar ion bombardment in BCl3/Cl2 plasma leaded to increased morphological surface roughening. The etch rate decreased with increasing O2 content owing to the O2 reaction with Ti and TiO2 layer formation on the surface. A nonvolatile etched byproduct was observed by XPS analysis. It could be estimated to be a Ti--Cl compound.
2011-08-25