Comparison of DC and RF Sputtered Zinc Oxide Films with Post-Annealing and Dry Etching and Effect on Crystal Composition

Zinc oxide (ZnO) thin films were deposited on Silicon substrates by DC and RF sputtering deposition. Thermal annealing was performed at up to 900°C in N2for 30 min. The samples were dry etched for 30 min using CHF3plasma. The effect of different sputtering techniques, annealing and reactive ion etching (RIE) were investigated using X-ray diffraction, Rutherford backscattering (RBS), photoluminescence (PL) spectra, atomic force microscopy (AFM), scanning electron microscopy (SEM), and piezoelectric measurements. The PL response improved considerably during annealing and was further enhanced after RIE process. RBS traced a C rich surface layer on all etched samples, which is possibly caused by the etching gas.