Dry etching of TiN in N2/Cl2/Ar adaptively coupled plasma

We investigated the N2 additive effect on the etch rates of TiN and SiO2 and etch profile of TiN in N2/Cl2/Ar adaptively coupled plasma (ACP). The mixing ratio of Cl2 and Ar was fixed at 75 and 25 sccm, respectively. The N2 flow rate was increased from 0 to 9 sccm under the constant pressure of 10 mTorr. As N2 flow rate was increased in N2/Cl2/Ar plasma, the etch rate of TiN was linearly increased, but that of SiO2 was increased non-monotonically. The etch profile and the compositional changes of TiN was investigated with field emission-scanning electron microscope (FE-SEM), FE-Auger electron spectroscopy (FE-AES) and x-ray photoelectron spectroscopy (XPS). When 9 sccm N2 was added into Cl2/Ar, a steep etch profile and clean surface of TiN was obtained. In addition, the signals of TiN and Ti were disappeared in FE-AES and XPS when N2 additive flow into Cl2/Ar was above 6 sccm. From the experimental data, the increase in TiN etch rate was mainly caused by the increase of desorption and evacuation rate of etch by products because of the increased effective pumping speed. The etch mechanism of TiN in N2/Cl2/Ar ACP plasma can be concluded as the ion enhanced chemical etch.

► TiN thin film was etched by an adoptively coupled plasma system.
► The N2 additive flow in N2/Cl2/Ar plasma plays important rule on a etch rate, a profile, and a surface of TiN.
► As N2 flow rate was increased, TiN etch rate was increased.
► The clean and steep etch profile was obtained at N2(9sccm)/Cl2/Ar condition, where Ti and N were not detected in FE-AES and XPS.