Damage on the Surface of Zinc Oxide Thin Films Etched in Cl-based Gas Chemistry

We investigated the etching characteristics of zinc oxide (ZnO) thin films deposited by the atomic layer deposition method. The gases of the inductively coupled plasma chemistry consisted of $Cl_2$, Ar, and $O_2$. The maximum etch rate was 40.3 nm/min at a gas flow ratio of $Cl_2$/Ar=15:5 sccm, radio-frequency power of 600 W, bias power of 200 W, and process pressure of 2 Pa. We also investigated the plasma induced damage in the etched ZnO thin films using X-ray diffraction (XRD), atomic force microscopy and photoluminescence (PL). A highly oriented (100) peak was present in the XRD spectroscopy of the ZnO samples. The full width at half maximum value of the ZnO sample etched using the $O_2/Cl_2$/Ar chemistry was higher than that of the as-deposited sample. The roughness of the ZnO thin films increased from 1.91 nm to 2.45 nm after etching in the $O_2/Cl_2$/Ar plasma chemistry. Also, we obtained a strong band edge emission at 380 nm. The intensities of the peaks in the PL spectra from the samples etched in all of the chemistries were increased. However, there was no deep level emission.