In this study, the plasma etching of the TaN thin film with $O_2/BCl_3$/Ar gas chemistries was investigated. The equipment for the etching was an inductively coupled plasma (ICP) system. The etch rate of the TaN thin film and the selectivity of TaN to $SiO_2$ and PR was studied as a function of the process parameters, including the amount of $O_2$ added, an RF power, a DC-bias voltage and the process pressure. When the gas mixing ratio was $O_2$(3 sccm)/$BCl_3$(6 sccm)/Ar(14 sccm), with the other conditions fixed, the highest etch rate was obtained. As the RF power and the dc-bias voltage were increased, the etch rate of the TaN thin film was increased. X-ray photoelectron spectroscopy (XPS) was used to investigate the chemical states of the surface of the TaN thin film.